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    November 09

    The Refined Lives of the F- and H-Vectors of Associahedra

    The compositional inversions noted in the Oct. 9-th entry "Flipping
    Functions with Permutohedra" have counterparts with respect to the
    associahedra, or Stasheff polytopes. The h-polynomials of the
    associahedra (see the Narayana number triangle OEIS-A001263) can be
    refined as OEIS-A134264 for the coefficients of an indirect Lagrange
    method for determining the compositional inverse of a function,
    whereas the corresponding f-polynomials (see OEIS-A033282) can be
    refined as the unsigned polynomials in OEIS-A133437 (or A111785) for
    the coefficients of a Lagrange inversion for an ordinary generating
    function. (OEIS denotes the Online Encyclopedia of Integer Sequences.)

    October 09

    Flipping Functions with Permutohedra

    Flipping Functions with Permutohedra A short note on forming the multiplicative and compositional inverses of functions using the refined Eulerian h-polynomials and refined face polynomials of permutohedra.

    September 28

    Combinatorics of OEIS-A074060

    The notes Combinatorics of OEIS-A074060 sketch how combinatorial interpretations of LaGrange inversion and the 2-restricted Stirling numbers of the first kind provide a combinatorial construction for the array OEIS-A074060 (Graded dimension of the cohomology ring of the moduli space of n-pointed curves of genus 0 satisfying the associativity equations of physics).

    September 13

    Short Note on Lagrange Inversion

     Short Note on Lagrange Inversion is an addendum to OEIS-A134685.

    June 12

    Mathemagical Forests

    The set of notes Mathemagical Forests is an expansion of the May notes and discusses some connections between rooted trees, derivative operators, Lagrange inversion, the Legendre transformation, the Faa di Bruno formula, Sheffer sequences and umbral calculus, and the infinite Witt Lie algebra.

    May 09

    A Walk in the Woods with Cayley and Comtet

    In the last several months, I've been exploring the connections between umbral calculus and integer sequences and have published several items, searchable under the name Tom Copeland, in the Online Encyclopedia of Integer Sequences (OEIS). During the process, I became aware of the ubiquitousness of trees in combinatorics and found it useful to go back to the origins to get a good feel for them. The resulting set of notes "A Walk in the Woods with Cayley and Comtet " might be a helpful introduction to others on some elementary relations between the infinitesimal calculus and rooted trees ala Cayley.