a(n) = n*(3*n-1)*n!/2.

A138782

a(n) = n*(3*n-1)*n!/2.

Terms

    a(0) =1a(1) =10a(2) =72a(3) =528a(4) =4200a(5) =36720a(6) =352800a(7) =3709440a(8) =42456960a(9) =526176000a(10) =7025356800a(11) =100590336000

External references