a(n) = n*(17*n + 1)/2.

Terms

a(0) =0a(1) =9a(2) =35a(3) =78a(4) =138a(5) =215a(6) =309a(7) =420a(8) =548a(9) =693a(10) =855a(11) =1034a(12) =1230a(13) =1443a(14) =1673a(15) =1920a(16) =2184a(17) =2465a(18) =2763a(19) =3078a(20) =3410a(21) =3759a(22) =4125a(23) =4508a(24) =4908a(25) =5325a(26) =5759a(27) =6210a(28) =6678a(29) =7163