First subdiagonal of number array A082137.

Terms

a(0) =1a(1) =3a(2) =20a(3) =140a(4) =1008a(5) =7392a(6) =54912a(7) =411840a(8) =3111680a(9) =23648768a(10) =180590592a(11) =1384527872a(12) =10650214400a(13) =82158796800a(14) =635361361920