There’s a Math Stack Exchange question: “Conjectures that have been disproved with extremely large counterexamples?” Maybe some of the examples in the answers over there would count? For example, there’s Euler’s sum of powers conjecture, which only has large counterexamples (for high k), found via ~brute force search.
There’s a Math Stack Exchange question: “Conjectures that have been disproved with extremely large counterexamples?” Maybe some of the examples in the answers over there would count? For example, there’s Euler’s sum of powers conjecture, which only has large counterexamples (for high k), found via ~brute force search.