Column 6 of triangle A055898.

Terms

a(0) =1a(1) =13a(2) =106a(3) =615a(4) =2850a(5) =11087a(6) =37626a(7) =114177a(8) =315805a(9) =807520a(10) =1930600a(11) =4354140a(12) =9331560a(13) =19117980a(14) =37630440a(15) =71461368a(16) =131399829a(17) =234661713a(18) =408100330a(19) =692741335a(20) =1150092658a(21) =1870787919a(22) =2986277658a(23) =4684437485a(24) =7230182505