a(n) = n! * Sum_{k=0..floor(n/3)} n^k * binomial(n-2*k,k)/(n-2*k)!.

A362301

a(n) = n! * Sum_{k=0..floor(n/3)} n^k * binomial(n-2*k,k)/(n-2*k)!.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =19a(4) =97a(5) =301a(6) =13681a(7) =124951a(8) =647809a(9) =46543897a(10) =612367201a(11) =4447574011a(12) =436897375201

External references