a(n) = (4*n)!/(3*n+1)!.

A365340

a(n) = (4*n)!/(3*n+1)!.

Terms

    a(0) =1a(1) =1a(2) =8a(3) =132a(4) =3360a(5) =116280a(6) =5100480a(7) =271252800a(8) =16963914240

External references