Number of positive integers <= 2^n of form x^2 + 18 y^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =4a(5) =9a(6) =15a(7) =28a(8) =51a(9) =94a(10) =177a(11) =329a(12) =624a(13) =1180a(14) =2253a(15) =4318a(16) =8285a(17) =15984a(18) =30872a(19) =59824a(20) =116113a(21) =225769a(22) =439726a(23) =857599a(24) =1674693a(25) =3274082a(26) =6407312a(27) =12550839a(28) =24605967a(29) =48277606