First differences of A237262.

Terms

a(0) =1a(1) =4a(2) =9a(3) =32a(4) =71a(5) =252a(6) =559a(7) =1984a(8) =4401a(9) =15620a(10) =34649a(11) =122976a(12) =272791a(13) =968188a(14) =2147679a(15) =7622528a(16) =16908641a(17) =60012036a(18) =133121449a(19) =472473760a(20) =1048062951a(21) =3719778044a(22) =8251382159a(23) =29285750592a(24) =64962994321a(25) =230566226692a(26) =511452572409