№8 — #813

from itertools import product
count = 0
for digits in product('0123456', repeat=5):
    if digits[0] == '0':
        continue
    s = ''.join(digits)
    if s.count('6') == 1:
        ok = all(s[j] != s[j+1] for j in range(4))
        if ok:
            count += 1
print(count)