a(n) = 5*n^2 - 1.

Terms

a(0) =4a(1) =19a(2) =44a(3) =79a(4) =124a(5) =179a(6) =244a(7) =319a(8) =404a(9) =499a(10) =604a(11) =719a(12) =844a(13) =979a(14) =1124a(15) =1279a(16) =1444a(17) =1619a(18) =1804a(19) =1999a(20) =2204a(21) =2419a(22) =2644a(23) =2879a(24) =3124a(25) =3379a(26) =3644a(27) =3919a(28) =4204a(29) =4499