Number of positive integers <= 2^n of the form x^2 + 5*y^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =7a(5) =13a(6) =22a(7) =40a(8) =73a(9) =132a(10) =245a(11) =458a(12) =864a(13) =1638a(14) =3123a(15) =5979a(16) =11484a(17) =22140a(18) =42773a(19) =82865a(20) =160809a(21) =312659a(22) =608857a(23) =1187323a(24) =2318344a(25) =4531879a(26) =8867913a(27) =17369053a(28) =34048772a(29) =66799240