a(n) = n! * (1 + Sum_{k=0..n} binomial(k+1,2) / k!).

A368762

a(n) = n! * (1 + Sum_{k=0..n} binomial(k+1,2) / k!).

Terms

    a(0) =1a(1) =2a(2) =7a(3) =27a(4) =118a(5) =605a(6) =3651a(7) =25585a(8) =204716a(9) =1842489a(10) =18424945a(11) =202674461a(12) =2432093610a(13) =31617217021a(14) =442641038399

External references