Three times second hexagonal numbers: 3*n*(2*n+1).

Terms

a(0) =0a(1) =9a(2) =30a(3) =63a(4) =108a(5) =165a(6) =234a(7) =315a(8) =408a(9) =513a(10) =630a(11) =759a(12) =900a(13) =1053a(14) =1218a(15) =1395a(16) =1584a(17) =1785a(18) =1998a(19) =2223a(20) =2460a(21) =2709a(22) =2970a(23) =3243a(24) =3528a(25) =3825a(26) =4134a(27) =4455a(28) =4788a(29) =5133