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

A362300

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

Terms

    a(0) =1a(1) =1a(2) =1a(3) =7a(4) =33a(5) =101a(6) =1681a(7) =14211a(8) =72577a(9) =1906633a(10) =23242401a(11) =166218911a(12) =5966236321a(13) =95016917997a(14) =873707885233

External references