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Brignall, Robert and Marchant, David William
(2018).
DOI: https://doi.org/10.1016/j.disc.2018.02.012
Abstract
We show that the Möbius function of an interval in a permutation poset where the lower bound is sum (resp. skew) indecomposable depends solely on the sum (resp. skew) indecomposable permutations contained in the upper bound, and that this can simplify the calculation of the Möbius sum. For increasing oscillations, we give a recursion for the Möbius sum which only involves evaluating simple inequalities.