Square-placement Wilf-equivalence conjecture for three length-four patterns

For a distant pattern, write a square between two consecutive letters to indicate the constrained gap at that position. Consider the classical patterns 12341234, 12431243, and 21432143, and choose the same one of the three positions between consecutive letters in each pattern. Square-placement Wilf-equivalence conjecture. The resulting three distant patterns are Wilf-equivalent; for example,

Avn(1234)=Avn(1243)=Avn(2143).|\operatorname{Av}_{n}(1\square 234)|=|\operatorname{Av}_{n}(1\square 243)|=|\operatorname{Av}_{n}(2\square 143)|.

The paper calls this conjecture surprising and notes that an analogous assertion for arbitrary Wilf-equivalent classical patterns is false, giving a counterexample in length four. It remains open in the stated special case.

Sources & referencesView supporting material

Primary source

Stoyan Dimitrov, “On permutation patterns with constrained gap sizes”, arXiv:2002.12322 (2021).

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