Sum of terms in each group in A074147.

Terms

a(0) =1a(1) =6a(2) =15a(3) =36a(4) =65a(5) =114a(6) =175a(7) =264a(8) =369a(9) =510a(10) =671a(11) =876a(12) =1105a(13) =1386a(14) =1695a(15) =2064a(16) =2465a(17) =2934a(18) =3439a(19) =4020a(20) =4641a(21) =5346a(22) =6095a(23) =6936a(24) =7825a(25) =8814a(26) =9855a(27) =11004a(28) =12209a(29) =13530