a(n) = 9*n^2 + 21*n - 6 (n>=1).

Terms

a(0) =24a(1) =72a(2) =138a(3) =222a(4) =324a(5) =444a(6) =582a(7) =738a(8) =912a(9) =1104a(10) =1314a(11) =1542a(12) =1788a(13) =2052a(14) =2334a(15) =2634a(16) =2952a(17) =3288a(18) =3642a(19) =4014a(20) =4404a(21) =4812a(22) =5238a(23) =5682a(24) =6144a(25) =6624a(26) =7122a(27) =7638a(28) =8172a(29) =8724