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bibkey: oeis2025a000166 authors: OEIS Foundation Inc.; Zhi-Wei Sun year: 2025 title: OEIS A000166, subfactorial or rencontres numbers doi: null url: https://oeis.org/A000166 claim: Zhi-Wei Sun comments that for n greater than 2 a(n) is a perfect power only at n = 4, with a(4) = 3^2, checked through n = 1000. strata_touched:

  • D5/S3/Arith/Derangements/DerangementTwoAdicValuation license: citation-only triage: anchor

OEIS A000166, subfactorial or rencontres numbers

The entry identifies A000166 with the derangement numbers. A comment by Zhi-Wei Sun dated January 9, 2025 states: “a(n) with n > 2 is a perfect power only for n = 4 with a(4) = 3^2” and records verification through n <= 1000.

This finite-range comment is context for the formal exponent-divisibility consequence. It is not treated as a proof of a universal perfect-power classification, and the repository theorem does not assert that only D_4 is a perfect power.

Search log

  • 2026-09-10: Directly inspected the public entry and its internal page for the comment text, attribution, date, and finite verification range.

Verified locator

  • https://oeis.org/A000166
  • https://oeis.org/A000166/internal