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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =4a(7) =8a(8) =14a(9) =26a(10) =48a(11) =87a(12) =162a(13) =303a(14) =569a(15) =1076a(16) =2044a(17) =3903a(18) =7485a(19) =14401a(20) =27778a(21) =53724a(22) =104135a(23) =202242a(24) =393450a(25) =766556a(26) =1495546a(27) =2921307a(28) =5712535a(29) =11181823