Iterator skips index 16?!

Hi Gents. Anyway seen something like this?

I'm failing on the "check solution" part. Here is what my code is:

number_sequence = [-37, -36, -19, -99, 29, 20, 3, -7, -64, 84, 36, 62, 26, -76, 55, -24, 84, 49, -65, 41]

def checkio(array): summ = 0 for i in array: if (array.index(i)) % 2 == 0: summ = summ + i print('index: ', array.index(i), 'element:', i ) if len(array) >= 1: product = summ * array[-1] else: product = 0 return product print(checkio(numbersequence)) print(numbersequence[16]) print(16%2)

And the result:

%Run ciorna.py index: 0 element: -37 index: 2 element: -19 index: 4 element: 29 index: 6 element: 3 index: 8 element: -64 index: 10 element: 36 index: 12 element: 26 index: 14 element: 55 index: 18 element: -65 -1476 84 0

What is going on? Why does the iterator skip over 16?