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

Terms

a(0) =0a(1) =8a(2) =33a(3) =75a(4) =134a(5) =210a(6) =303a(7) =413a(8) =540a(9) =684a(10) =845a(11) =1023a(12) =1218a(13) =1430a(14) =1659a(15) =1905a(16) =2168a(17) =2448a(18) =2745a(19) =3059a(20) =3390a(21) =3738a(22) =4103a(23) =4485a(24) =4884a(25) =5300a(26) =5733a(27) =6183a(28) =6650a(29) =7134