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

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =4a(5) =7a(6) =12a(7) =21a(8) =38a(9) =69a(10) =126a(11) =234a(12) =437a(13) =825a(14) =1565a(15) =2982a(16) =5710a(17) =10967a(18) =21138a(19) =40842a(20) =79099a(21) =153510a(22) =298435a(23) =581095a(24) =1133110a(25) =2212231a(26) =4324045a(27) =8460649a(28) =16570079a(29) =32480219