a(n) = n*(14*n - 11).

Terms

a(0) =0a(1) =3a(2) =34a(3) =93a(4) =180a(5) =295a(6) =438a(7) =609a(8) =808a(9) =1035a(10) =1290a(11) =1573a(12) =1884a(13) =2223a(14) =2590a(15) =2985a(16) =3408a(17) =3859a(18) =4338a(19) =4845a(20) =5380a(21) =5943a(22) =6534a(23) =7153a(24) =7800a(25) =8475a(26) =9178a(27) =9909a(28) =10668a(29) =11455