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%I #14 Apr 07 2021 12:22:36
%S 1,8,34,142,596,2530,10842,46766,202594,880210
%N Number of rationally smooth Schubert varieties of type B_n.
%C 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.
%D S. Billey, Pattern avoidance and rational smoothness of Schubert varieties, Advances in Math, vol. 139 (1998) pp. 141-156.
%Y Cf. A061539.
%K nonn,hard,more
%O 1,2
%A _Sara Billey_, Apr 01 2013
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