Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%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