Number of functions f:{1,2,...,2n}->{1,2,...,2n} such that every preimage has an even cardinality.

A209289

Number of functions f:{1,2,...,2n}->{1,2,...,2n} such that every preimage has an even cardinality.

Terms

    a(0) =1a(1) =2a(2) =40a(3) =2256a(4) =250496a(5) =46063360a(6) =12665422848

External references