A347393 Positions of 3's in A347381.
7, 10, 11, 14, 16, 18, 25, 27, 39, 45, 63, 77, 81, 99, 105, 135, 182, 270, 819, 1365, 1392, 1638, 4250, 15631, 21275, 63767, 122944, 161257, 203203, 446369, 936100, 1128799, 1773827, 2808300
Offset: 1
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