Column 2 of triangle A127126.

Terms

a(0) =1a(1) =3a(2) =18a(3) =139a(4) =1314a(5) =14658a(6) =188012a(7) =2721462a(8) =43837014a(9) =777266691a(10) =15037898091a(11) =315177210360