A subdiagonal of number array A082137.

Terms

a(0) =1a(1) =4a(2) =30a(3) =224a(4) =1680a(5) =12672a(6) =96096a(7) =732160a(8) =5601024a(9) =42997760a(10) =331082752a(11) =2556051456a(12) =19778969600a(13) =153363087360