a(n) = (6*n)!/((4*n)!*n!) * (n/2)!/(3*n/2)!.

A347856

a(n) = (6*n)!/((4*n)!*n!) * (n/2)!/(3*n/2)!.

Terms

    a(0) =1a(1) =20a(2) =990a(3) =56576a(4) =3432198a(5) =215147520a(6) =13768454700a(7) =893768826880

External references