W-0069

A superpermutation on 12 symbols, found by William Echols. It beat the previous record, W-0066, by 1 letter, and was the record for n = 12 from Oct 17 until Oct 18, 2026, when W-0071 was 1 letter shorter.

Length: 522,737,174
Repeated occurrences: 177,465
Announced: Oct 17, 2026

Begins

0123456789AB0123456789A0B123456789A01B23456789A012B3456789A0123B456789A01234B56789A012345B6789A0123456B789A01234567B89A0…

Windows

	522,737,163	windows of 12 consecutive letters
=	479,001,600	distinct permutations, all 12! of them
+	177,465	repeated occurrences of a permutation
+	43,558,098	windows that are not permutations

How it was found

Found with GPT-6 Pro by shortening Halfar's 522,737,175 by one letter; relabelled from 0-9, A, B to 1-9, A, B, C (NOTICE beside the file).

Checking

Total check time: 9 s, including preparation but not time in the queue.

Program	Source	Result	Time
classcheck	41928cce	all 479,001,600 permutations appear, by rotation class	3 s
bitmapcheck	288b3f67	agrees, by Lehmer rank	2 s
wordhash	94925fe4	the SHA-256 of the word and of its mirror	3 s

SHA-25610fad08c4fe6c55e4456a5f6d347f93394318338c8cae24d7f98912689a4d2ff Compilerrustc 1.89.0 (29483883e 2025-08-04)

Download

Download Detour (.detour) 59.5 kB, or 522.7 MB decoded

Decode to text

# check it yourself
detour decode W-0069.detour - | tr -d '\n' | shasum -a 256
tar xzf checkers-rs-source.tar.gz && cd checkers-rs && cargo build --release --locked
./target/release/classcheck 12 ../W-0069.detour 522737174
./target/release/bitmapcheck 12 ../W-0069.detour 522737174
./target/release/wordhash 12 ../W-0069.detour 522737174

Decoding needs detour; see the Detour format for how to build and install it. The checkers are in checkers-rs-source.tar.gz, which needs Rust 1.89 or later; each one decodes the file itself, so the word is never written out.

The file's header gives n = 12 and sync exponent 0. The file has 5,193,985 tokens: 1 START, 1 literal of 1 byte in all, and 5,193,983 deviations. Deviations by weight, from 1 to 12: 177,465 · 1,409,797 · 3,605,005 · 284 · 120 · 843 · 99 · 137 · 186 · 28 · 19 · 0.