  We prove a conjecture due to Wanless about the permanent of Hadamard matrices
in the particular case of Sylvester-Hadamard matrices. Namely we show that for
all n greater or equal to 2, the dyadic valuation of the permanent of the
Sylvester-Hadamard matrix of order n is equal to the dyadic valuation of n!. As
a consequence, the permanent of the Sylvester-Hadamard matrix of order n
doesn't vanish for n greater or equal to 2.
