Partial sums of A027818.

Terms

a(0) =0a(1) =1a(2) =15a(3) =99a(4) =435a(5) =1485a(6) =4257a(7) =10725a(8) =24453a(9) =51480a(10) =101530a(11) =189618a(12) =338130a(13) =579462a(14) =959310a(15) =1540710a(16) =2408934a(17) =3677355a(18) =5494401a(19) =8051725a(20) =11593725a(21) =16428555a(22) =22940775a(23) =31605795a(24) =43006275a(25) =57850650a(26) =76993956a(27) =101461140a(28) =132473044a(29) =171475260