3 times 9-gonal (or nonagonal) numbers: a(n) = 3*n*(7*n-5)/2.

Terms

a(0) =0a(1) =3a(2) =27a(3) =72a(4) =138a(5) =225a(6) =333a(7) =462a(8) =612a(9) =783a(10) =975a(11) =1188a(12) =1422a(13) =1677a(14) =1953a(15) =2250a(16) =2568a(17) =2907a(18) =3267a(19) =3648a(20) =4050a(21) =4473a(22) =4917a(23) =5382a(24) =5868a(25) =6375a(26) =6903a(27) =7452a(28) =8022a(29) =8613