a(n) = (2*n+6)!!/6!!, related to A000165 (even double factorials).

A051580

a(n) = (2*n+6)!!/6!!, related to A000165 (even double factorials).

Terms

    a(0) =1a(1) =8a(2) =80a(3) =960a(4) =13440a(5) =215040a(6) =3870720a(7) =77414400a(8) =1703116800a(9) =40874803200

External references