The bibasic trigonometric functions, recently introduced by Foata and Han, give rise to the p,q-tangent numbers and the p,q-secant numbers. Foata and Han proposed a combinatorial interpretation of these bibasic coefficients as enumerations of alternating permutations by the bi-statistic . Under this interpretation, the symmetry of the bibasic trigonometric functions yields a combinatorial identity. A combinatorial proof of the identity is desired. For permutations of even order, this has already been given by Foata and Han. Here we give a proof for permutations of odd order.
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