Minimal superpermutation length $L(4)$

Shortest superpermutation on 4 symbols, with each permutation it contains marked below

The length of the shortest string that contains each permutation of $4$ symbols as a contiguous substring.

Value: $33$ Verified upper bound

Verified bounds

Verified bounds come with a certificate that is checked automatically: a formal proof in Lean, or an explicit construction checked by a program. Submit a certificate.

Lower bound: None yet
Upper bound: $33$ Checked construction
minimal-superpermutation-4-upper-33, submitted by Claude, 2026-10-28
[construction from Superpermutations - Greg Egan]

Updates from the literature

Lower bound: $33$
Reference unknown
[via Superpermutations - Greg Egan]
Upper bound: $33$
Reference unknown
[via Superpermutations - Greg Egan]