A054171 Number of positive integers <= 2^n of form 4 x^2 + 7 y^2.

0, 0, 1, 2, 4, 7, 12, 23, 41, 77, 142, 270, 504, 958, 1834, 3505, 6752, 13016, 25170, 48775, 94718, 184210, 358805, 699919, 1366853, 2672452, 5230345, 10245791, 20088113, 39415538, 77394348, 152067981, 298975703, 588143637, 1157617442