Column 2 of triangle A318945.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =6a(6) =26a(7) =97a(8) =331a(9) =1064a(10) =3277a(11) =9775a(12) =28448a(13) =81201a(14) =228211a(15) =633384a(16) =1740037a(17) =4740327a(18) =12825008a(19) =34500649a(20) =92372683a(21) =246352952a(22) =654878173a(23) =1736172895a(24) =4592568896a(25) =12125944161a(26) =31967715811a(27) =84170419272a(28) =221388694261a(29) =581807602839