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Shadows of Simplicity

Explorations on connections between various areas of mathematics. A work in progress on the interplay between the umbral and fractional calculus, special functions, combinatorics and mathematical physics.
11月9日

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.)

10月9日

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.

9月28日

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).

6月12日

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.