a(n) = 52*n^2 - 1.

Terms

a(0) =51a(1) =207a(2) =467a(3) =831a(4) =1299a(5) =1871a(6) =2547a(7) =3327a(8) =4211a(9) =5199a(10) =6291a(11) =7487a(12) =8787a(13) =10191a(14) =11699a(15) =13311a(16) =15027a(17) =16847a(18) =18771a(19) =20799a(20) =22931a(21) =25167a(22) =27507a(23) =29951a(24) =32499a(25) =35151a(26) =37907a(27) =40767a(28) =43731a(29) =46799