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

A356029

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

Terms

    a(0) =1a(1) =1a(2) =1a(3) =4a(4) =13a(5) =61a(6) =421a(7) =2626a(8) =27049a(9) =245953a(10) =3069721a(11) =40222216a(12) =576988501a(13) =10058716669a(14) =169773404893

External references