A224255 Number of permutations w in S_n whose Kazhdan-Lusztig polynomial evaluated at q=1 is less than or equal to 2; P_{id,w}(1) <= 2.

1, 2, 6, 24, 115, 590, 3050, 15576, 78318, 388208

Offset

1,2

Comments

This family of permutations is characterized by a finite set of patterns.

References

S. Billey and T. Braden, Lower bounds for Kazhdan-Lusztig polynomials from patterns, Transform. Groups 8 (2003), no. 4, 321-332.

Links

Table of n, a(n) for n=1..10.

FindStat - Combinatorial Statistic Finder, The evaluation of the Kazhdan-Lusztig polynomial P(id,w) for each permutation w in S_n evaluated at q = 1

A. Woo, Permutations with Kazhdan-Lusztig polynomial P_{id,w}(q) = 1 + q^h with appendix by Sara Billey and Jonathan Weed, The Electronic Journal of Combinatorics, Volume 16(2), 2009.

Crossrefs

Cf. A224316.

Sequence in context: A177522 A216717 A174072 * A326348 A128088 A069657

Adjacent sequences: A224252 A224253 A224254 * A224256 A224257 A224258

Keyword

nonn,more

Author

Sara Billey, Apr 03 2013

Status

approved