46063360

Appears in sequences

• Number of functions f:{1,2,...,2n}->{1,2,...,2n} such that every preimage has an even cardinality.at n=5A209289
• Triangular array read by rows: T(n,k) is the number of f:{1,2,...,n}->{1,2,...,n} with exactly 2k elements that have a preimage of even (possibly zero) cardinality; n>=0, 0<=k<=floor(n/2).at n=35A225942