"What does f(n) count?" - in search for a paper - MathOverflow most recent 30 from http://mathoverflow.net 2013-06-20T04:34:28Z http://mathoverflow.net/feeds/question/38541 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/38541/what-does-fn-count-in-search-for-a-paper "What does f(n) count?" - in search for a paper Hans Stricker 2010-09-13T06:28:17Z 2010-09-13T09:40:17Z <p>I am desperately searching for a paper I once have read, but cannot find anymore. It was about a counting function f(n) - the only thing I remember is that f's expression contained n! and 2<sup>n</sup> - and the question in the title was something like "What does f(n) count?". The paper compared three or so different approaches, and was written as a trialog.</p> <blockquote> <p>Can someone point me to this paper?</p> </blockquote> <p>If you know about other papers on this question - "What does f(n) count?", with f(n) any counting-but-what function, I'd be happy to learn about them. </p> http://mathoverflow.net/questions/38541/what-does-fn-count-in-search-for-a-paper/38550#38550 Answer by Hans Stricker for "What does f(n) count?" - in search for a paper Hans Stricker 2010-09-13T09:25:59Z 2010-09-13T09:25:59Z <p>One question of this kind can be found on MO: </p> <p><a href="http://mathoverflow.net/questions/9220/what-does-the-generating-function-x-1-e-x-count" rel="nofollow">What does the generating function \$x/(1 - e^{-x})\$ count?</a></p> http://mathoverflow.net/questions/38541/what-does-fn-count-in-search-for-a-paper/38552#38552 Answer by vool for "What does f(n) count?" - in search for a paper vool 2010-09-13T09:40:17Z 2010-09-13T09:40:17Z <p>Could it be <a href="http://dx.doi.org/10.2307/2589493" rel="nofollow"><em>The answer is \$2^n·n\$! What's the question?</em></a> by Gary Gordon (Amer. Math. Monthly <strong>106</strong> (1999), no. 7, 636&ndash;645)?</p>