a(n) = n! * Sum_{k=0..floor(n/2)} k^(2*n)/k!.

A357193

a(n) = n! * Sum_{k=0..floor(n/2)} k^(2*n)/k!.

Terms

    a(0) =1a(1) =0a(2) =2a(3) =6a(4) =3096a(5) =61560a(6) =65248200a(7) =4058986680

External references