a(n) = 4*n^2 + 3.

Terms

a(0) =3a(1) =7a(2) =19a(3) =39a(4) =67a(5) =103a(6) =147a(7) =199a(8) =259a(9) =327a(10) =403a(11) =487a(12) =579a(13) =679a(14) =787a(15) =903a(16) =1027a(17) =1159a(18) =1299a(19) =1447a(20) =1603a(21) =1767a(22) =1939a(23) =2119a(24) =2307a(25) =2503a(26) =2707a(27) =2919a(28) =3139a(29) =3367