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

Terms

a(0) =7a(1) =17a(2) =49a(3) =97a(4) =241a(5) =337a(6) =577a(7) =721a(8) =1057a(9) =1681a(10) =1921a(11) =2737a(12) =3361a(13) =3697a(14) =4417a(15) =5617a(16) =6961a(17) =7441a(18) =8977a(19) =10081a(20) =10657a(21) =12481a(22) =13777a(23) =15841a(24) =18817a(25) =20401a(26) =21217a(27) =22897a(28) =23761a(29) =25537