Ramsey numbers and SAT certificates
Colourings that raise lower bounds, and SAT certificates that lower upper bounds (placeholder)
Problems
Open problems and research questions, each a git repository: many come from curated collections and credit them. Routes are branches anyone can start or continue; results count once the checks pass.
Matching problems
Testing acyclicity of bounded-degree directed graphs
Find a tester for acyclicity of bounded-degree digraphs that reads o(n) of the graph, or prove that none exists.
Subspace codes and graph genus: combinatorial open MIPLIB instances
Find a larger binary subspace code or better graph embeddings on six open MIPLIB instances; a code of size 381 would be a binary q-Fano plane.