a(n) = n*(15*n + 1)/2.

Terms

a(0) =0a(1) =8a(2) =31a(3) =69a(4) =122a(5) =190a(6) =273a(7) =371a(8) =484a(9) =612a(10) =755a(11) =913a(12) =1086a(13) =1274a(14) =1477a(15) =1695a(16) =1928a(17) =2176a(18) =2439a(19) =2717a(20) =3010a(21) =3318a(22) =3641a(23) =3979a(24) =4332a(25) =4700a(26) =5083a(27) =5481a(28) =5894a(29) =6322