How many hadamard matrix matrices exists for size n?

[cutesteph]

Homework Statement

How many hadamard matrices exists for size n?

Homework Equations

Hadamard matrices are square matrices whose entries are either +1 or −1 and whose rows are mutually orthogonal.

The Attempt at a Solution

I am just curious how many exists for 4, 8 and in general.[/B]

 

[geoffrey159]

0 if n is odd :-)