Number of positive integers <= 2^n of form x^2 + 3 y^2.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =8a(5) =14a(6) =25a(7) =45a(8) =82a(9) =151a(10) =282a(11) =531a(12) =1003a(13) =1907a(14) =3645a(15) =6993a(16) =13456a(17) =25978a(18) =50248a(19) =97446a(20) =189291a(21) =368338a(22) =717804a(23) =1400699a(24) =2736534a(25) =5352182a(26) =10478044a(27) =20531668a(28) =40264582a(29) =79022464