a(n) = 441*n^2 + 21.

Terms

a(0) =21a(1) =462a(2) =1785a(3) =3990a(4) =7077a(5) =11046a(6) =15897a(7) =21630a(8) =28245a(9) =35742a(10) =44121a(11) =53382a(12) =63525a(13) =74550a(14) =86457a(15) =99246a(16) =112917a(17) =127470a(18) =142905a(19) =159222a(20) =176421a(21) =194502a(22) =213465a(23) =233310a(24) =254037a(25) =275646a(26) =298137a(27) =321510a(28) =345765a(29) =370902