In combinatorics, a Stirling number of the second kind (or Stirling partition number) is the number of ways to partition a set of n objects into k non-empty subsets and is denoted by S(n,k)1. This online calculator calculates Stirling number of the second kind for the given n, for each k from 0 to n and outputs results into a table. Note that this calculator uses "big integers" library (see Tips and tricks #9: Big numbers), so you can try pretty big n values.
For example, the number of ways to partition a set of 100 objects into 28 non-empty subsets is 7769730053598745155212806612787584787397878128370115840974992570102386086289805848025074822404843545178960761551674. Combinatorial explosion, that is :)
For those who curious, explicit formula is listed below the calculator
Stirling numbers formula
Ronald L. Graham, Donald E. Knuth, Oren Patashnik (1988) Concrete Mathematics, Addison–Wesley, Reading MA. ISBN 0-201-14236-8, p. 244. ↩