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

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =5a(5) =10a(6) =17a(7) =33a(8) =58a(9) =109a(10) =202a(11) =379a(12) =720a(13) =1369a(14) =2618a(15) =5031a(16) =9701a(17) =18766a(18) =36387a(19) =70688a(20) =137572a(21) =268208a(22) =523581a(23) =1023425a(24) =2002829a(25) =3923400a(26) =7692930a(27) =15096706a(28) =29649082a(29) =58270386