A simple combinatorial proof of a generalization
of a result of Polo


We provide a simple combinatorial proof of, and generalize, a theorem
of Polo which asserts that for any polynomial P with nonnegative integer
coefficients such that P(0)=1 there exist two permutations u and v in a
suitable symmetric group such that P is equal to the Kazhdan-Lusztig
polynomial P_u,v.

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