Column 2 of triangle A152798; first differences of A122889.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =15a(5) =40a(6) =113a(7) =348a(8) =1148a(9) =4045a(10) =15203a(11) =60710a(12) =256688a(13) =1145887a(14) =5386283a(15) =26590338a(16) =137537012a(17) =743766652a(18) =4196681423a(19) =24661702224a(20) =150676068558a(21) =955611495432