Binomial matrix: an N-by-N multiple of an involutory matrix with
integer entries such that $A^2 = 2^(N-1)*I_N$
Thus B = A*2^((1-N)/2) is involutory, that is B^2 = EYE(N)
Usage
binomial_matrix(n)
Value
a binomial matrix, which is a multiple of involutory matrix