def f(s, m):

    if s >= 51: return m % 2 == 0

    if m == 0: return 0

    h = [f(s + 1, m - 1), f(s + 4, m - 1), f(s * 2, m - 1)]

    return any(h) if m % 2 != 0 else all(h)

print('19)', [s for s in range(1, 51) if f(s, 2)])
print('20)', [s for s in range(1, 51) if not f(s, 1) and f(s, 3)])
print('21)', [s for s in range(1, 51) if not f(s, 2) and f(s, 4)])