Column 3 of triangle A135880.

Terms

a(0) =1a(1) =4a(2) =26a(3) =216a(4) =2171a(5) =25628a(6) =348050a(7) =5352788a(8) =92056223a(9) =1752149568a(10) =36591725976a(11) =832352590164