## Task:

Your task is to write a function which returns the sum of following series upto nth term(parameter).

    Series: 1 + 1/4 + 1/7 + 1/10 + 1/13 + 1/16 +...
 
## Rules:
 
* You need to round the answer to 2 decimal places and return it as String.

* If the given value is 0 then it should return 0.00

* You will only be given Natural Numbers as arguments.

## Examples:

    SeriesSum(1) => 1 = "1.00"
    SeriesSum(2) => 1 + 1/4 = "1.25"
    SeriesSum(5) => 1 + 1/4 + 1/7 + 1/10 + 1/13 = "1.57"
    
**NOTE**: In PHP the function is called `series_sum()`.

Difficulty: introductory

Starter code:

def series_sum(n):
	

Solutions:
def series_sum(n):
    return '{:.2f}'.format(sum(1.0/(3 * i + 1) for i in range(n)))

def series_sum(n):
    sum = 0.0
    for i in range(0,n):
        sum += 1 / (1 + 3 * float(i))
    return '%.2f' % sum

def series_sum(n):
    seriesSum = 0.0
    for x in range(n):
        seriesSum += 1 / (1 + x * 3)
    return '%.2f' % seriesSum

def series_sum(n):
  return "%.2f" % sum([1.0 / (3 * i + 1) for i in range(n)])

def series_sum(n):
    a=0
    for i in range(n):
        a+=1/(3*i+1)
    return "{:.2f}".format(a)
    
        


from fractions import Fraction
def series_sum(n):
    total = sum(Fraction(1, 1 + i * 3) for i in range(n))
    return '{:.2f}'.format(total.numerator / total.denominator)

def series_sum(n):
    return f'{sum(1/d for d in range(1,n*3,3)):.2f}'

def series_sum(n):
  return "%.2f" % sum(map(lambda x: x**-1, range(1,3*n,3)))

def series_sum(n):
    sum=0
    for i in range(n):
        sum+=1/(1+3*i)
    return '%.2f' % sum

print((series_sum(0)))


def series_sum(n):
    result = 0
    for i in range(0, n):
        result += (1 / (1+3*i))
    return "{number:.{digits}f}".format(number=result, digits=2)

series_sum = lambda n: '{:.2f}'.format(sum(1.0/(3*i-2) for i in range(1, n+1)))


series_sum = lambda n: '{:.2f}'.format(round(sum( 1/(1+(e)*3) for e in range(n) ) ,2))

def series_sum(n):
    return "{0:.2f}".format(sum([1. / (1 + 3*x)for x in range(n)]))

def series_sum(n):
    total = 0
    for i in range(n):
        total += 1/(1+ i*3)
    return str('%.2f' % total)

def series_sum(n):
    return '%.2f' % sum(1.0 / (3 * i + 1) for i in range(n))


def series_sum(n):
    return "{0:.2f}".format( sum(1.0/(1+(i-1)*3) for i in range(1,n+1)) )

def series_sum(n):
    return f"{sum(1/x for x in range(1,(n*3)-1,3)):.2f}"

def series_sum(number):
  solution = sum((1 / (1 + 3 * i) for i in range(number)))
  return format(solution, '.2f')

def series_sum(n):
    return f"{n and sum(1 / i for i in range(1, n*3+1, 3)):.2f}"


from fractions import Fraction
from functools import lru_cache

@lru_cache(maxsize=None)
def rec(n):
    if not n: return 0
    return Fraction(1, 3*n-2) + rec(n-1)

# This is overkill for this kata
def series_sum(n):
    return f"{float(rec(n)):.2f}"

def series_sum(n):
    # Happy Coding ^_^
    sum=0.00
    if n==1:
        return("1.00")
    elif n==0:
        return("0.00")
    else:
        denominator=1.00
        for i in range(0,n):
            if (i+1) <= n:
                sum=sum+(1/denominator)
                denominator=denominator + 3.00
    
    return(str(format(round(sum,2),'.2f')))

def series_sum(n):
  return '%.2f' % sum(1/x for x in range(1, n*3+1, 3))

def series_sum(n):
    sum = 0
    for i in range(1, n * 3, 3):
        sum += 1 / i
    return "{:.2f}".format(sum)


def series_sum(n):
    l=[]
    if n==0:
        x = '0.00'
    while n>0:
        l.append(1/(1+3*(n-1)))
        n-=1
        x = '%.2f' % sum(l)
    return x

def series_sum(n):
    # Happy Coding ^_^
    return '%0.2f' % (
        round (
            sum([1/(1+(x-1)*3) for x in range(1, n+1)]), 2
            )
        )

def series_sum(n):
    if n == 0:
        return '0.00'
    else:
        x = 1
        sum = 0
        for i in range(n):
            sum += 1/(x)
            x += 3
        
        
        s = "{:0.2f}".format(sum)
        return s


def series_sum(n):
    sum = 0
    for i in range(0, n):
        sum += 1/(1+i*3)
    return str(format(sum, '.2f'))

def series_sum(n):
    return "{0:.2f}".format(round(sum(1.0/(1+3*m) for m in range(n)), 2)) if n else "0.00"

def series_sum(n):
    return "%.2f" %(sum(1/(1+3*x) for x in range(n)))

def series_sum(n):
    sum = 0
    for i in range(0, n):
        sum += 1.0 / (i * 3 + 1)
    return "%.2f" % sum

def series_sum(n):
    if n == 0:
        return '0.00'
    return '%0.2f' % float(str(1 + sum(1/(1+i*3) for i in range(1,n))))

def series_sum(n):
    return format(sum(1/(1+3*k) for k in range(n)),'.2f')

def series_sum(n):
    ls = []
    if(n == 0): return str("%5.2f" % 0.00)[1:]
    for n in range(1,n):
        ls.append(1/(1+(n*3)))
    return str("%5.2f" % (float(sum(ls)+1)))[1:]

def series_sum(n):
    sum = 0
    for x in range(n):
        sum = sum + 1/(3 * x + 1)
    return "%.2f" % sum

def series_sum(n):
    return "%.2f" % sum([1/(1+(3*t)) for t in range(n)])

def series_sum(n):
    result = 0
    for i in range(0,n):
        result += 1.00/(1 + (3 * i))
    stringresult = str(round(result, 2))
    if stringresult == '0':
        stringresult = '0.00'
    while len(stringresult) < 4:
        stringresult += '0'
    return stringresult


def series_sum(n):
    float_sum = sum([1/(i*3.0+1) for i in range(n)])
    return '%.2f' % float_sum

def series_sum(n):
    return '{:.2f}'.format(sum(1.0/d for d in range(1, n*3, 3)))

def series_sum(n):
    if n==0: return "0.00"
    elif n==1: return "1.00"
    
    sum = 1.0
    for i in range(1,n):
        sum += 1/(1+3*i)
    return '%.2f' % sum

def series_sum(n):
    sum = 0
    for i in range(n):
        sum += 1/(1+3*i)
    return("%.2f" % sum)


def series_sum(n):
    x = 0
    y = 1
    for n in range(1, n+1):
        x = x + y
        y = 1/((1/y)+3)
        n = n - 1
    return format(x, '.2f')

def series_sum(n):
    sum_ = sum([1 / (i*3-2) for i in range(1, n+1)])
    return '%.2f' % sum_

from decimal import Decimal

def series_sum(n):
    if n == 0:
        sum_ = 0
    else:
        sum_ = 1
        for i in range(n-1):
            nth_value = 1 / (4+3*i)
            sum_ += nth_value

    sum_str = str(round(Decimal(sum_), 2))
    return sum_str

def series_sum(n):
    return "{0:.2f}".format(sum([(1+3*(k-1))**-1 if k>0 else k for k in range(n+1)]))

def series_sum(n):
    return '%.2f'%series_sum_(n)
    
def series_sum_(n):
    if(n>1):
        return series_sum_(n-1)+float(float(1.00)/float(3*(n-1)+1))
    elif(n==1):
        return float(1.00)
    return float(0.00)


def series_sum(n):
    total = 0
    for num in range(1, n+1):
        total += (1/(1+(3*(num-1))))
    return "%.2f" % total


def series_sum(n):
    # Happy Coding ^_^
    f = 3 * n - 2
    s = 0
    if n == 0:
        return "0.00"
    for i in range(1, f + 1, 3):
        s = s + (1 / i)
    return "{:.2f}".format(s)

def series_sum(n):
    sum = 0
    div = 1

    for i in range(n):
        sum += 1/div
        div += 3
    if n == 0 :
        return str(n)+'.00'
    elif len(str(round(sum,2)))<4:
       return str(round(sum,2))+"0"
    else:
       return str(round(sum,2))


def series_sum(n):
    # Happy Coding ^_^
    sum = 0;
    if(n == 1):
        return "1.00"
    else:
        for i in range(n):
            sum += 1/(1+3*i)
    return str("%.2f" % sum)

def series_sum(n):
    # term = 3n+1
    if n == 0:
        term = 0
    elif n>0:
        term = 1
        for i in range(1,n):
            term += 1/(3*i+1)
        sumterm = float("{:.2f}".format(term))
    return "%0.2f" % term

def series_sum(n):
    if n == 0:
        return("0.00")
    else:
        counter = 1
        list = [1]
        while counter < n:
            list.append(1 / (1 + (3 * counter)))
            counter += 1
        flt = round((sum(list)), 2)
        result = format(flt, ".2f")
        return(result)

def series_sum(n):
    ans = 0
    while n != 0:
        ans += 1 / (3 * n - 2)
        n -= 1
    return "{:.2f}".format(round(ans,2)).__str__()

def series_sum(n):
    if n == 0:
        return '0.00'
    final = 0
    x = 0
    while n >= 1:
        final += 1/(1+x)
        x += 3
        n -= 1
    final = str(final)
    if len(final) < 4:
        final += '0'
    if len(final) > 4:
        if int(final[4]) > 4:
            final = str(float(final) +.01)
    return str(final)[:4]

def series_sum(n):
    summa = sum([1/(1+3*x) for x in range(n)])
    return f"{summa:.{2}f}"

def series_sum(n=0):
    # Happy Coding ^_^
    sum=0.00
    num=1
    for i in range(n):
        sum+=1/num
        num+=3
    return ((str(round(sum,2)))+"0")[:4]


def series_sum(n):
    # Happy Coding ^_^
    a=0
    for i in range(0,n):
        a+=1/(1+i*3)
    return '{:.2f}'.format(a)
    


def series_sum(n):
    return "%1.2f" % sum((1 / x) for x in range(1 ,3 * n ,3))

def series_sum(n):
    x=1 
    s=0
    for i in range(n):
       
        s+= 1/(x+i*3)
    if s==0:
        return '0.00'
    if len(str(round(s,2))) <4:
        return str(round(s,2))+'0'
    
    return str(round(s,2))

def series_sum(n):
    if n == 0:
        return "0.00"
    if n == 1 :
        return "1.00"
    elif n== 2:
        return "1.25"
    else :
        sum =1.25
        i = 4
        for loop in range(n-2):
            i = i+3
            sum = sum + 1/i
    return "{:.2f}".format(sum)
            


def series_sum(n):
    result = 1+1/4
    a = 4
    if n==1:
        return str('%.2f'%n)
    elif n == 0:
        return str('%.2f'%0)
    for i in range(1,n-1):
        result+=1/(a+i*3)
    return str('%.2f'%result)

def series_sum(n):
    res = sum(1/(3*d+1) for d in range(n))
    return f'{res:.2f}'

def series_sum(n):
    answer = 0
    for number in range(n):
        answer += 1 / (1 + (number * 3))
    return(str(format(answer, '.2f')))

def series_sum(n):
    i = 1
    x = 0
    
    for a in range(n):
        x += 1/i
        i += 3
            
    return '{:.2f}'.format(x)

def series_sum(n):
    output = 0
    for i in range(n):
        output += 1/(1+(i*3))
    if len(str(round(output,2))) < 4:
        if str(round(output,2)) != "0":
            a = str(round(output,2))
            a += "0"
            return a
        else: return  "0.00"
    else:
        return str(round(output,2))

def series_sum(n):
    if n == 0:
        return "0.00"
    if n== 1:
        return "1.00"
    sum = 1.00
    for i in range(n-1):
        sum=sum+1/(4+(3*i))
    return "{:.2f}".format(sum)


import decimal
def series_sum(n):
    return "%.2f" % sum(1 / (1 + 3 * i) for i in range(n))

import math
def series_sum(n):
    # Happy Coding ^_^
    result = 0.00
    for i in (list(range(0, n))): 
        result += 1.00 / (1.00 + (3.00 * float(i)) )
    return "{:.2f}".format(result)
    
    


def series_sum(n):
    if n == 0:
        return('0.00')
    else:
        numerator = 1
        denom = 1
        output = ''
        num = 0.00 
        for i in range(n):
            num += (numerator / denom)
            denom += 3
            output = str(format(round(num,2),'.2f'))
        return(output)

from fractions import Fraction
def series_sum(n):
    
    sum=0
    
    for i in range(n):
        sum+=1/(1+i*3)
    
    return format(sum,'.2f')

def series_sum(n):
    total = 0
    for i in range(n):
        total += 1 / (3 * i + 1)
    return f"{total:.2f}"

def series_sum(n):
    return (str(round(1+sum(1/x for x in range(4,n*3,3)),2)) if n>1 else str(float(n))).ljust(4,"0")

def series_sum(n):
    s = 1
    i = 1
    if n > 1:
        while i < n:
            s = 1/(1+(i*3)) + s
            i += 1
    else:
        return str('%.2f' % n)
    return str('%.2f' % s)
            


def series_sum(n):
    n = n - 1
    return f'{sum(1/i for i in range(1,2+3*n,3)):.2f}'

def series_sum(n):
    array = []
    for i in range(n):
        array.append(1/(1 + 3 * i))
    return f'{sum(array):.2f}'

def series_sum(n):
    sum = 0.00
    denom = 1.00
    for i in range(1,n+1):
        sum = sum + 1/denom
        denom = denom + 3.00
        
    return f'{sum:.2f}'

def series_sum(n):
    series = 0
    for i in range(0, n):
        series += 1 / (1 + 3 * i)
    return "{:.2f}".format(series)

def series_sum(n):
    denom = 1
    total = 0.00
    count = 0
    while count < n:
        total = total + 1/denom
        count = count + 1
        denom = denom + 3
        print(("%.2f" % total))
    return "%.2f" % total
    
        
    
            
            


def series_sum(n):
    sum = 1
    if n > 1:
        for i in range(n - 1):
            sum += (1 / (4 + (3 * i)))
    return str("{:.2f}".format(round(sum,2))) if n > 0 else "0.00"


def series_sum(n):
    # Happy Coding ^_^
    sum = float()
    j = 1
    for i in range(n):
        sum += (1/j)
        j += 3
    result = str(round(sum, 2))
    if len(result) == 3:
        return result+'0'
    else:
        return result
        


def series_sum(n):
    return "{:.2f}".format(sum([1 / i for i in range(1, n * 3 + 1, 3)]))

def series_sum(n):
    # Happy Coding ^_^
    x = 1
    s = 0
    for i in range(n):
        s += 1/x
        x += 3
    return "{:.2f}".format(s)

def series_sum(n):
    if n == 0:
        return "0.00"
    d = 1
    ans = 0
    for i in range(n):
        ans += 1/d
        d += 3
    ans = f"{round(ans, 2)}"
    return ans if len(ans) == 4 else ans + "0" * (4 - len(ans))

def series_sum(n):
    sum = 1.00
    if n == 1:
        return('1.00')
    elif n==0: return('0.00')
    else:
        for x in range(1,n):
            sum = sum + (1/((2*(x+1))+(x-1)))
        return("{:.2f}".format(sum))
    


def series_sum(n):
    if (n == 0): return '0.00'
    sum = 1.0
    count = 4
    for i in range(n-1):
        sum += 1/count
        count += 3
    return "{:.2f}".format(sum, 2)

def series_sum(n):
    sum=0.00
    value=1.00
    if n==0:
        return format(sum,".2f")
    for i in range(1,n+1):
        sum=sum+(1/value)
        value+=3
    result=float("{0:.2f}".format(sum))
    return format(sum,".2f")


def series_sum(n):
    y = str(round(sum([ 1 / x for x in range(1, n * 3 + 1, 3)]), 2))
    while len(y) < 4:
        y += "0"
    return "0.00" if n == 0 else y

def series_sum(n):
    return str('%.2f' % sum([1/(1 + 3 * x) for x in range(n)]))

def series_sum(n):
    
    if n == 0:
        return '0.00'
    elif n == 1:
        return '1.00'
    else:
        s = 1
        a = [1]
        for i in range(n):
            s += 3
            a.append(1/s)
        a[-1] = 0
        a = str((round(sum(a),2)))
        if len(a) == 4:
            return a
        else:
            b = a+ '0'
            return b