a(n) = 64*n^2 - 1.

Terms

a(0) =63a(1) =255a(2) =575a(3) =1023a(4) =1599a(5) =2303a(6) =3135a(7) =4095a(8) =5183a(9) =6399a(10) =7743a(11) =9215a(12) =10815a(13) =12543a(14) =14399a(15) =16383a(16) =18495a(17) =20735a(18) =23103a(19) =25599a(20) =28223a(21) =30975a(22) =33855a(23) =36863a(24) =39999a(25) =43263a(26) =46655a(27) =50175a(28) =53823a(29) =57599