A125756 Numbers n whose reverse binary representation has the following property: let a 0 mean "halving" and a 1 mean "k -> 3k+1". The number describes an operation k -> f_n(k). If the equation f_n(k) = k has a positive integer solution, n is a term in the sequence.

4, 36, 140, 145, 200, 292, 1059, 1136, 1553, 1800, 2340, 4150, 4274, 4297, 4308, 4389, 4433, 4490, 4634, 4696, 4705, 4741, 4804, 4876, 5133, 5164, 5218, 5254, 5400, 5409, 5668, 5712, 5761, 6244, 6290, 6312, 6448, 6466, 6662, 6800, 6976