What is next in the number sequence?

Question

Two and two is four,
But three and three is nine;
Four and four is eighty,
But five and five is none.

What is the next line in the sequence?

Answer 1

They are

multiples of the squares of the numbers. (2x2x1, 3x3x1, 4x4x5, 5x5x0)

So the question becomes

what case does 6 fall under

I'll go with

the cases are the square mod 5, since the squares, and five, are involved anyway. The three cases correspond to -1, +1, and 0 mod 5. So 2^2 and 3^2 are both negative, and 5^2 is zero, while 4^2 and 6^2 are both positive.

So

six and six is one hundred and eighty.