Number of positive integers <= 2^n of form x^2 + 19 y^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =4a(5) =9a(6) =15a(7) =29a(8) =52a(9) =96a(10) =179a(11) =336a(12) =640a(13) =1218a(14) =2338a(15) =4507a(16) =8706a(17) =16874a(18) =32808a(19) =63863a(20) =124599a(21) =243437a(22) =476164a(23) =932611a(24) =1828498a(25) =3588303a(26) =7047954a(27) =13853566a(28) =27250355a(29) =53636267