a(n) = A000272(n+1) * A000984(n).

A227325

a(n) = A000272(n+1) * A000984(n).

Terms

    a(0) =1a(1) =2a(2) =18a(3) =320a(4) =8750a(5) =326592a(6) =15529668a(7) =899678208a(8) =61556811030

External references