Number of positive integers <= 2^n of form x^2 + 20 y^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =4a(5) =9a(6) =14a(7) =26a(8) =47a(9) =85a(10) =158a(11) =295a(12) =552a(13) =1048a(14) =2000a(15) =3829a(16) =7373a(17) =14216a(18) =27505a(19) =53378a(20) =103728a(21) =201981a(22) =393900a(23) =769192a(24) =1503947a(25) =2943906a(26) =5767973a(27) =11311511a(28) =22200845a(29) =43605974