3 times 12-gonal (or dodecagonal) numbers: a(n) = 3*n*(5*n-4).

Terms

a(0) =0a(1) =3a(2) =36a(3) =99a(4) =192a(5) =315a(6) =468a(7) =651a(8) =864a(9) =1107a(10) =1380a(11) =1683a(12) =2016a(13) =2379a(14) =2772a(15) =3195a(16) =3648a(17) =4131a(18) =4644a(19) =5187a(20) =5760a(21) =6363a(22) =6996a(23) =7659a(24) =8352a(25) =9075a(26) =9828a(27) =10611a(28) =11424a(29) =12267