Column 3 of triangle A117418.

Terms

a(0) =1a(1) =4a(2) =14a(3) =50a(4) =191a(5) =780a(6) =3415a(7) =15924a(8) =78595a(9) =408337a(10) =2224365a(11) =12650992a(12) =74876950a(13) =459783611a(14) =2922921341a(15) =19192162340a(16) =129864598566a(17) =903840021981