Number of positive integers <= 2^n of form x^2 + 13 y^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =6a(5) =10a(6) =19a(7) =32a(8) =58a(9) =105a(10) =194a(11) =364a(12) =682a(13) =1295a(14) =2467a(15) =4723a(16) =9059a(17) =17448a(18) =33706a(19) =65256a(20) =126643a(21) =246179a(22) =479336a(23) =934603a(24) =1824646a(25) =3566467a(26) =6978040a(27) =13666391a(28) =26788334a(29) =52551600