Buggy python submission (verdict: Time Limit Exceeded):
import sys
n = int(input())
s = list(input())
a_li = []
b_li = []
c_li = []
for i,ss in enumerate(s):
    if ss == 'R':
        a_li.append(i+1)
    elif ss == 'G':
        b_li.append(i+1)
    else:
        c_li.append(i+1)
if len(a_li) == 0 or len(b_li)== 0 or len(c_li) == 0:
    print(0)
    sys.exit()
#all_count = 0
""" for a in a_li:
    for b in b_li:
        tmp = len(c_li)
        if (2*b - a)  in c_li:
            #lili.append(2*b - a)
            tmp -= 1
        if (2*a - b)  in c_li:
            #lili.append(2*a - b)
            tmp -= 1
        if (a + b)% 2 == 0 and (a + b)//2   in c_li:
            #lili.append((a + b)//2)
            tmp -= 1
        #tmp -= len(set(lili))
        all_count += tmp
print(all_count) """

#print(a_li,b_li,c_li)
all_count = 0
for i in range(1,n-1):
    for j in range(i+1,n):
        for k in range(j+1,n+1):
            if j-i == k-j:
                continue
            else:
                if i in a_li and j in b_li and k in c_li:
                    all_count += 1
                if i in a_li and j in c_li and k in b_li:
                    all_count += 1
                if i in b_li and j in a_li and k in c_li:
                    all_count += 1
                if i in b_li and j in c_li and k in a_li:
                    all_count += 1
                if i in c_li and j in a_li and k in b_li:
                    all_count += 1
                if i in c_li and j in b_li and k in a_li:
                    all_count += 1
print(all_count)

Fixed submission:
n = int(input())
s = list(input())
a_li = []
b_li = []
c_li = []
for i,ss in enumerate(s):
    if ss == 'R':
        a_li.append(i+1)
    elif ss == 'G':
        b_li.append(i+1)
    else:
        c_li.append(i+1)
count = 0
for i in range(1,n+1):
    for d in range(1,n):
        if i + 2*d > n:
            break
        if s[i-1] != s[i+d-1] and s[i+d-1] != s[i+2*d-1] and s[i-1] != s[i+2*d-1]:
            count += 1
#print(len(a_li),len(b_li),len(c_li),count)
#print(count)
print(len(a_li)*len(b_li)*len(c_li)-count)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
n = int(input())
s = list(input())
a_li = []
b_li = []
c_li = []
for i,ss in enumerate(s):
    if ss == 'R':
        a_li.append(i)
    elif ss == 'G':
        b_li.append(i)
    else:
        c_li.append(i)
if len(a_li) == 0 or len(b_li)== 0 or len(c_li) == 0:
    print(0)
    sys.exit()
all_count = 0
for a in a_li:
    for b in b_li:
        tmp = len(c_li)
        if (2*b - a)  in c_li:
            #lili.append(2*b - a)
            tmp -= 1
        if (2*a - b)  in c_li:
            #lili.append(2*a - b)
            tmp -= 1
        if (a + b)% 2 == 0 and (a + b)//2   in c_li:
            #lili.append((a + b)//2)
            tmp -= 1
        #tmp -= len(set(lili))
        all_count += tmp
print(all_count)

Fixed submission:
n = int(input())
s = list(input())
a_li = []
b_li = []
c_li = []
for i,ss in enumerate(s):
    if ss == 'R':
        a_li.append(i+1)
    elif ss == 'G':
        b_li.append(i+1)
    else:
        c_li.append(i+1)
count = 0
for i in range(1,n+1):
    for d in range(1,n):
        if i + 2*d > n:
            break
        if s[i-1] != s[i+d-1] and s[i+d-1] != s[i+2*d-1] and s[i-1] != s[i+2*d-1]:
            count += 1
#print(len(a_li),len(b_li),len(c_li),count)
#print(count)
print(len(a_li)*len(b_li)*len(c_li)-count)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
n = int(input())
s = list(input())
a_li = []
b_li = []
c_li = []
for i,ss in enumerate(s):
    if ss == 'R':
        a_li.append(i)
    elif ss == 'G':
        b_li.append(i)
    else:
        c_li.append(i)
if len(a_li) == 0 or len(b_li)== 0 or len(c_li) == 0:
    print(0)
    sys.exit()
all_count = 0
for a in a_li:
    for b in b_li:
        tmp = len(c_li)
        lili = []
        if (2*b - a)  in c_li:
            lili.append(2*b - a)
            #tmp -= 1
        if (2*a - b)  in c_li:
            lili.append(2*a - b)
            #tmp -= 1
        if (a + b)% 2 == 0 and (a + b)//2   in c_li:
            lili.append((a + b)//2)
            #tmp -= 1
        tmp -= len(set(lili))
        all_count += tmp
print(all_count)

Fixed submission:
n = int(input())
s = list(input())
a_li = []
b_li = []
c_li = []
for i,ss in enumerate(s):
    if ss == 'R':
        a_li.append(i+1)
    elif ss == 'G':
        b_li.append(i+1)
    else:
        c_li.append(i+1)
count = 0
for i in range(1,n+1):
    for d in range(1,n):
        if i + 2*d > n:
            break
        if s[i-1] != s[i+d-1] and s[i+d-1] != s[i+2*d-1] and s[i-1] != s[i+2*d-1]:
            count += 1
#print(len(a_li),len(b_li),len(c_li),count)
#print(count)
print(len(a_li)*len(b_li)*len(c_li)-count)