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

A347854

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

Terms

    a(0) =1a(1) =40a(2) =4620a(3) =622336a(4) =89237148a(5) =13236695040

External references