Column 2 of triangle A152391.

Terms

a(0) =1a(1) =3a(2) =8a(3) =40a(4) =216a(5) =1386a(6) =9552a(7) =71820a(8) =571440a(9) =4815778a(10) =42465144a(11) =391058720a(12) =3738272328a(13) =37015339410a(14) =378307524768