a(n) = 8*n^2 - 1.

Terms

a(0) =7a(1) =31a(2) =71a(3) =127a(4) =199a(5) =287a(6) =391a(7) =511a(8) =647a(9) =799a(10) =967a(11) =1151a(12) =1351a(13) =1567a(14) =1799a(15) =2047a(16) =2311a(17) =2591a(18) =2887a(19) =3199a(20) =3527a(21) =3871a(22) =4231a(23) =4607a(24) =4999a(25) =5407a(26) =5831a(27) =6271a(28) =6727a(29) =7199