Column 7 of triangle A055898.

Terms

a(0) =1a(1) =15a(2) =141a(3) =939a(4) =4971a(5) =21981a(6) =84351a(7) =287961a(8) =891564a(9) =2539756a(10) =6733764a(11) =16769916a(12) =39526524a(13) =88722756a(14) =190653804a(15) =393952284a(16) =785736369a(17) =1517620599a(18) =2846653381a(19) =5198360739a(20) =9261986019a(21) =16131790389a(22) =27513326919a(23) =46020006201