a(n) = 54*n^2 - 78*n + 36.

Terms

a(0) =36a(1) =12a(2) =96a(3) =288a(4) =588a(5) =996a(6) =1512a(7) =2136a(8) =2868a(9) =3708a(10) =4656a(11) =5712a(12) =6876a(13) =8148a(14) =9528a(15) =11016a(16) =12612a(17) =14316a(18) =16128a(19) =18048a(20) =20076a(21) =22212a(22) =24456a(23) =26808a(24) =29268a(25) =31836a(26) =34512a(27) =37296a(28) =40188a(29) =43188