a(n) = A154796(n)/2.

Terms

a(0) =15a(1) =28a(2) =88a(3) =245a(4) =396a(5) =979a(6) =1505a(7) =3421a(8) =44567a(9) =62377a(10) =225638a(11) =307077a(12) =415910a(13) =1006279a(14) =4059132a(15) =6924325a(16) =66615465a(17) =107240563a(18) =135624475a(19) =270973120a(20) =425688314a(21) =663855038a(22) =1581563676a(23) =2417635935a(24) =2982269752a(25) =3673314756a(26) =4517918038a(27) =5548822508a(28) =8335344604a(29) =15194335989