most recent 30 from http://mathoverflow.net 2013-05-26T00:52:36Z http://mathoverflow.net/feeds/question/38044 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/38044/about-generalization-of-stirling-numbers-of-the-second-kind Eduardo Lopez 2010-09-08T11:03:42Z 2010-09-08T11:03:42Z

<p>Hello,</p> <p>The Stirling numbers of the second kind count how many ways can a set of $k$ elements be partitioned into $n$ non-empty classes, with $k=n,n+1,\dots$. </p> <p>My question is: Is there a generalization of these numbers such that the classes are not merely non-empty, but instead occupied to a minimum level with each of the $n$ classes having a minimum of, say, $r$ elements in it? Of course, in this case, $k=rn,rn+1,\dots$.</p>