a(n) = 6*n^2 + 1.

Terms

a(0) =1a(1) =7a(2) =25a(3) =55a(4) =97a(5) =151a(6) =217a(7) =295a(8) =385a(9) =487a(10) =601a(11) =727a(12) =865a(13) =1015a(14) =1177a(15) =1351a(16) =1537a(17) =1735a(18) =1945a(19) =2167a(20) =2401a(21) =2647a(22) =2905a(23) =3175a(24) =3457a(25) =3751a(26) =4057a(27) =4375a(28) =4705a(29) =5047