Comparing the numbers of subforests and subgraph-degree-tuples
Abstract
We enumerate the row-column-sums of all square tridiagonal -matrices and prove that their count coincides with OEIS A022026 the number of acyclic subgraphs of the complete grid graph. We then extend this correspondence in two independent directions: 1. admitting larger sets of matrix entries, and 2. relaxing the tridiagonal support to broader prescribed sparsity patterns. The latter leads us to conjecture that, for any bipartite graph , the number of its acyclic subgraphs equals the number of degree sequences realized by subgraphs of . Moreover, for any non-bipartite graph, the former should be strictly smaller than the latter. We discuss several general approaches and prove these hypotheses for cactus graphs and generalized book graphs.
Keywords
Cite
@article{arxiv.2510.26936,
title = {Comparing the numbers of subforests and subgraph-degree-tuples},
author = {Sergei Shteiner and Pavel Shteyner},
journal= {arXiv preprint arXiv:2510.26936},
year = {2025}
}
Comments
24 pages