034-6kyu-Tribonacci Sequence.py

def tribonacci(signature, n):
    if n == 0:
        return []
    if n < 3:
        return [signature[i] for i in range(0,n)]
    res = signature[:]
    for i in range(3,n):
        res.append(res[i-1] + res[i-2] + res[i-3])
    return res