A054153 Number of positive integers <= 2^n of form x^2 + 9 y^2.

1, 1, 2, 2, 6, 8, 18, 30, 57, 103, 194, 360, 682, 1292, 2464, 4721, 9078, 17481, 33808, 65485, 127116, 247179, 481426, 938950, 1833572, 3584679, 7015237, 13741715, 26940645, 52858250, 103785060, 203913141, 400891200, 788601863, 1552114600