Sums of terms of groups in A075621.

Terms

a(0) =1a(1) =6a(2) =15a(3) =35a(4) =63a(5) =114a(6) =177a(7) =255a(8) =369a(9) =510a(10) =671a(11) =867a(12) =1122a(13) =1373a(14) =1692a(15) =2046a(16) =2477a(17) =2916a(18) =3444a(19) =4012a(20) =4641a(21) =5336a(22) =6092a(23) =6936a(24) =7805a(25) =8814a(26) =9855a(27) =10983a(28) =12230a(29) =13503