A Grammatical Calculus for the Ramanujan Polynomials
Abstract
The Ramanujan polynomials arise in three intertwined contexts. As remarked by BerndtEvans-Wilson, no combinatorial perspective seems to be alluded to in the original definition of Ramanujan. On a different stage, Dumont-Ramamonjisoa uncovered a combinatorial structure underneath an equation also considered by Ramanujan. Around the same time, Shor came up with the same construction as a refinement of the classical formula of Cayley for trees. We present a labeling scheme for rooted trees by employing an extra label marking improper edges. Harnessed by this grammar, we develop a grammatical calculus for the Ramanujan polynomials heavily relying on the constant properties. Moreover, we provide a grammatical formulation of a correspondence that leads to the recurrence relation due to Berndt-Evans-Wilson and Shor.
Cite
@article{arxiv.2506.01649,
title = {A Grammatical Calculus for the Ramanujan Polynomials},
author = {William Y. C. Chen and Amy M. Fu and Elena L. Wang},
journal= {arXiv preprint arXiv:2506.01649},
year = {2026}
}
Comments
20 pages, 3 figures, to appear in Ramanujan J