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A224240
Number of rationally smooth Schubert varieties of type B_n.
1
1, 8, 34, 142, 596, 2530, 10842, 46766, 202594, 880210
OFFSET
1,2
COMMENTS
Also, the number of signed permutations w in the hyperoctahedral group whose initial interval [id,w] in Bruhat order is rank symmetric. Equivalently, the Kazhdan-Lusztig polynomial P_id,w(q) = 1. Characterized by pattern avoidance.
REFERENCES
S. Billey, Pattern avoidance and rational smoothness of Schubert varieties, Advances in Math, vol. 139 (1998) pp. 141-156.
CROSSREFS
Cf. A061539.
Sequence in context: A302083 A124843 A082840 * A101644 A126395 A335749
KEYWORD
nonn,hard,more
AUTHOR
Sara Billey, Apr 01 2013
STATUS
approved