Buggy python submission (verdict: Runtime Error):
import copy

def acgt_2(t):
    w = ["A","C","G","T"]
    string_list = []
    for i in range(4):
        a = t // (4**(3-i))
        t = t % (4**(3-i))
        s = w[a]
        string_list.append(s)
    
    def acgt_sw(inst,a,b):
        st = copy.deepcopy(inst)
        st[a], st[b] = st[b], st[a]
        return "".join(st)

    
    string_list_2 = ["".join(string_list)] + [acgt_sw(string_list,i,i+1) for i in range(3)] 
    judge = False
    for i in string_list_2:

        if i[:3] == "AGC":
            judge = True

        if i[1:] == "AGC":
            judge = True

    return judge, "".join(string_list)
        

mod = 10**9+7
ng_list = []
for i in range(256):
    if acgt_2(i)[0]:
        ng_list.append(i)



n = int(input())
if n == 3:
    ans = 61
else:
    dp_list = [ 1 for i in range(4**4) ]
    for i in ng_list:
        dp_list[i] = 0

    for i in range(n-4):
        new_dp_list = [ 0 for i in range(4**4) ]
        for j in range(4**4):
            base = dp_list[j]
            new_index = [ 4*(j % 64) + k for k in range(4) ]
            for k in new_index:
                new_dp_list[k] += base
        for j in ng_list:
            new_dp_list[j] = 0
            dp_list = [ i%mod for i in new_dp_list]

print(sum(dp_list)%mod)


Fixed submission:
import copy
def acgt_2(t):
    w = ["A","C","G","T"]
    string_list = []
    for i in range(4):
        a = t // (4**(3-i))
        t = t % (4**(3-i))
        s = w[a]
        string_list.append(s)
    
    def acgt_sw(inst,a,b):
        st = copy.deepcopy(inst)
        st[a], st[b] = st[b], st[a]
        return "".join(st)

    
    string_list_2 = ["".join(string_list)] + [acgt_sw(string_list,i,i+1) for i in range(3)] 
    judge = False
    for i in string_list_2:

        if i[:3] == "AGC":
            judge = True

        if i[1:] == "AGC":
            judge = True

    return judge, "".join(string_list)
        

mod = 10**9+7
ng_list = []
for i in range(256):
    if acgt_2(i)[0]:
        ng_list.append(i)



n = int(input())
if n == 3:
    ans = 61
else:
    dp_list = [ 1 for i in range(4**4) ]
    for i in ng_list:
        dp_list[i] = 0

    for i in range(n-4):
        new_dp_list = [ 0 for i in range(4**4) ]
        for j in range(4**4):
            base = dp_list[j]
            new_index = [ 4*(j % 64) + k for k in range(4) ]
            for k in new_index:
                new_dp_list[k] += base
        for j in ng_list:
            new_dp_list[j] = 0
            dp_list = [ i%mod for i in new_dp_list]
    ans = sum(dp_list)%mod

print(ans)

Buggy python submission (verdict: Runtime Error):

def acgt_2(t):
    w = ["A","C","G","T"]
    string_list = []
    for i in range(4):
        a = t // (4**(3-i))
        t = t % (4**(3-i))
        s = w[a]
        string_list.append(s)
    
    def acgt_sw(inst,a,b):
        st = copy.deepcopy(inst)
        st[a], st[b] = st[b], st[a]
        return "".join(st)

    
    string_list_2 = ["".join(string_list)] + [acgt_sw(string_list,i,i+1) for i in range(3)] 
    judge = False
    for i in string_list_2:

        if i[:3] == "AGC":
            judge = True

        if i[1:] == "AGC":
            judge = True

    return judge, "".join(string_list)
        

mod = 10**9+7
ng_list = []
for i in range(256):
    if acgt_2(i)[0]:
        ng_list.append(i)



n = int(input())
if n == 3:
    ans = 61
else:
    dp_list = [ 1 for i in range(4**4) ]
    for i in ng_list:
        dp_list[i] = 0

    for i in range(n-4):
        new_dp_list = [ 0 for i in range(4**4) ]
        for j in range(4**4):
            base = dp_list[j]
            new_index = [ 4*(j % 64) + k for k in range(4) ]
            for k in new_index:
                new_dp_list[k] += base
        for j in ng_list:
            new_dp_list[j] = 0
            dp_list = [ i%mod for i in new_dp_list]

print(sum(dp_list)%mod)

Fixed submission:
import copy
def acgt_2(t):
    w = ["A","C","G","T"]
    string_list = []
    for i in range(4):
        a = t // (4**(3-i))
        t = t % (4**(3-i))
        s = w[a]
        string_list.append(s)
    
    def acgt_sw(inst,a,b):
        st = copy.deepcopy(inst)
        st[a], st[b] = st[b], st[a]
        return "".join(st)

    
    string_list_2 = ["".join(string_list)] + [acgt_sw(string_list,i,i+1) for i in range(3)] 
    judge = False
    for i in string_list_2:

        if i[:3] == "AGC":
            judge = True

        if i[1:] == "AGC":
            judge = True

    return judge, "".join(string_list)
        

mod = 10**9+7
ng_list = []
for i in range(256):
    if acgt_2(i)[0]:
        ng_list.append(i)



n = int(input())
if n == 3:
    ans = 61
else:
    dp_list = [ 1 for i in range(4**4) ]
    for i in ng_list:
        dp_list[i] = 0

    for i in range(n-4):
        new_dp_list = [ 0 for i in range(4**4) ]
        for j in range(4**4):
            base = dp_list[j]
            new_index = [ 4*(j % 64) + k for k in range(4) ]
            for k in new_index:
                new_dp_list[k] += base
        for j in ng_list:
            new_dp_list[j] = 0
            dp_list = [ i%mod for i in new_dp_list]
    ans = sum(dp_list)%mod

print(ans)