Column 0 of triangle A123305.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =26a(5) =156a(6) =1234a(7) =12340a(8) =150994a(9) =2204112a(10) =37617314a(11) =738465620a(12) =16451763834a(13) =411281292920