Number of positive integers <= 2^n of form x^2 + 6 y^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =13a(6) =24a(7) =42a(8) =76a(9) =140a(10) =257a(11) =483a(12) =907a(13) =1717a(14) =3272a(15) =6261a(16) =12027a(17) =23172a(18) =44769a(19) =86708a(20) =168245a(21) =327073a(22) =636849a(23) =1241720a(24) =2424290a(25) =4738450a(26) =9271396a(27) =18157630a(28) =35591729a(29) =69820804