Diagonal of A056151.

Terms

a(0) =1a(1) =7a(2) =38a(3) =222a(4) =1464a(5) =10920a(6) =91440a(7) =851760a(8) =8749440a(9) =98340480a(10) =1201132800a(11) =15846969600a(12) =224651750400