Number of positive integers <= 2^n of form 4 x^2 + 9 y^2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =4a(5) =5a(6) =10a(7) =18a(8) =35a(9) =65a(10) =120a(11) =225a(12) =430a(13) =814a(14) =1549a(15) =2981a(16) =5739a(17) =11084a(18) =21474a(19) =41663a(20) =81033a(21) =157830a(22) =307912a(23) =601482a(24) =1176314a(25) =2302911a(26) =4513106a(27) =8851907a(28) =17376317a(29) =34134944