Permutation Sequence Observatory

Sequence Atlas

A359012

Proposed by John Samuel

Interactive cartography for a sparse, strange substring sequence.

A359012 tracks integers k that reappear inside xPy when k = concat(x, y). This site reads the canonical CSV directly and turns the dataset into an explorable visual atlas.

Field Guide

Quick hints for the sequence vocabulary

Witness

A witness is a permutation value P(x,y) that actually contains the term k as a substring.

Depth

Depth measures where k appears inside its witness. Near 0 means close to the start; near 1 means close to the end.

Expansion Ratio

The expansion ratio is |P(x,y)| / |k|, telling you how much longer the witness is than the term itself.

Split

A split breaks k into x and y. Different split lengths can produce very different witness behavior.

System Summary

What the dataset looks like at a glance

Length Profile

Term lengths are heavily concentrated at six digits

Length Distribution

Compare how often three-, four-, five-, and six-digit terms appear in the current dataset.

Split Geometry

A heatmap of (|x|, |y|) shows which digit splits dominate the sequence.

Sequence Growth

The cumulative curve tracks how quickly terms accumulate as k increases.

Witness Structure ?

Every point is a term in the sequence

Expansion vs Relative Depth ?

Dots are colored by term length. Horizontal position shows how much larger xPy is than k, while vertical position shows where k appears within the permutation value.

Depth Distribution

How uniformly does k land inside P(x,y)? Each bin covers a 10% slice of the witness length. A flat histogram would indicate no positional bias.

Log-Log Growth

Cumulative term count on log-log axes reveals the power-law density exponent α (count(N) ≈ C · Nα). A slope α < 1 confirms the sequence grows sub-linearly.

Spacing

Gaps between consecutive terms

Inter-Term Gap

Each bar is the gap from a term to its predecessor. Large spikes mark stretches of integers where no term qualifies — the sequence's deserts.

Sequence Browser

Filter and inspect the canonical rows

k x y |P(x,y)| ? Position ? Depth ? Ratio ? Digit sum Witnesses ?