Number of positive integers <= 2^n of form 4 x^2 + 7 y^2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =4a(5) =7a(6) =12a(7) =23a(8) =41a(9) =77a(10) =142a(11) =270a(12) =504a(13) =958a(14) =1834a(15) =3505a(16) =6752a(17) =13016a(18) =25170a(19) =48775a(20) =94718a(21) =184210a(22) =358805a(23) =699919a(24) =1366853a(25) =2672452a(26) =5230345a(27) =10245791a(28) =20088113a(29) =39415538