a(n) = 144*n^2 - 12.

Terms

a(0) =132a(1) =564a(2) =1284a(3) =2292a(4) =3588a(5) =5172a(6) =7044a(7) =9204a(8) =11652a(9) =14388a(10) =17412a(11) =20724a(12) =24324a(13) =28212a(14) =32388a(15) =36852a(16) =41604a(17) =46644a(18) =51972a(19) =57588a(20) =63492a(21) =69684a(22) =76164a(23) =82932a(24) =89988a(25) =97332a(26) =104964a(27) =112884a(28) =121092a(29) =129588