English

On a divisor of the central binomial coefficient

Combinatorics 2021-04-13 v2 Number Theory

Abstract

It is well known that for all n1n\geq1 the number n+1n+ 1 is a divisor of the central binomial coefficient (2nn){2n\choose n}. Since the nnth central binomial coefficient equals the number of lattice paths from (0,0)(0,0) to (n,n)(n,n) by unit steps north or east, a natural question is whether there is a way to partition these paths into sets of n+1n+ 1 paths or n+1n+1 equinumerous sets of paths. The Chung-Feller theorem gives an elegant answer to this question. We pose and deliver an answer to the analogous question for 2n12n-1, another divisor of (2nn){2n\choose n}. We then show our main result follows from a more general observation regarding binomial coefficients (nk){n\choose k} with nn and kk relatively prime. A discussion of the case where nn and kk are not relatively prime is also given, highlighting the limitations of our methods. Finally, we come full circle and give a novel interpretation of the Catalan numbers.

Keywords

Cite

@article{arxiv.2102.00944,
  title  = {On a divisor of the central binomial coefficient},
  author = {Matthew Just and Maxwell Schneider},
  journal= {arXiv preprint arXiv:2102.00944},
  year   = {2021}
}

Comments

16 pages, 11 figures, 1 table

R2 v1 2026-06-23T22:43:47.469Z