TribonacciSequence.py

def tribonacci(s, n):
    for i in range(3, n):
        s.append(s[i-1] + s[i-2] + s[i-3])
    return print(s[:n])
'''
Well met with Fibonacci bigger brother, AKA Tribonacci.

As the name may already reveal, it works basically like a Fibonacci,
but summing the last 3 (instead of 2) numbers of the sequence to generate
the next. And, worse part of it, regrettably I won't get to hear 
non-native Italian speakers trying to pronounce it 

So, if we are to start our Tribonacci sequence with [1, 1, 1] 
as a starting input (AKA signature), we have this sequence:

[1, 1 ,1, 3, 5, 9, 17, 31, ...]
But what if we started with [0, 0, 1] as a signature? As starting with [0, 1] 
instead of [1, 1] basically shifts the common Fibonacci sequence by once place, 
you may be tempted to think that we would get the same sequence shifted by 2 places,
but that is not the case and we would get:

[0, 0, 1, 1, 2, 4, 7, 13, 24, ...]
Well, you may have guessed it by now, but to be clear: you need to create a fibonacci 
function that given a signature array/list, returns the first n elements - signature 
included of the so seeded sequence.

Signature will always contain 3 numbers; n will always be a non-negative number; 
if n == 0, then return an empty array. '''