Hacker News new | ask | show | jobs
by obastani 1901 days ago
There is a subtle but important difference. To be more precise, consider the following two statements:

1) There exists some n such that all integers >= n satisfy the desired property.

2) For n = [a specific constant], all integers >= n satisfy the desired property.

These two statements are not the same, but both imply that there are a finite number of counterexamples. The second one is stronger, since we could prove the statement by enumerating all k < n and checking the statement for each such k; if all these checks pass, then the statement is correct.

This strategy does not work for the first strategy since we do not know n, only that such an n exists. In particular, there could be a non-constructive proof that establishes existence of such an n without providing any way to compute such an n.

From the discussion, it does sound like this paper is proving (2), not (1).

1 comments

Yup. You came in and said it before I could get back to this...