most recent 30 from http://mathoverflow.net 2013-05-22T12:38:01Z http://mathoverflow.net/feeds/user/17396 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/51531/theorems-that-are-obvious-but-hard-to-prove/73742#73742 Paul 2011-08-26T07:48:44Z 2011-08-26T07:48:44Z

<p>I'm not sure if it is considered obvious, but I think the Collatz conjecture is also a good example (not just hard to prove, but still unproven!). I've always found it very frustrating that such a simple conjecture does not lend itself to a simple proof.</p> <p>'Obvious' here sort of means: Try a lot of values, and you'll get a feeling THAT it indeed holds, but also WHY it holds.</p> <p><a href="http://en.wikipedia.org/wiki/Collatz_conjecture" rel="nofollow">http://en.wikipedia.org/wiki/Collatz_conjecture</a></p>