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Consider I have a set of $3$ object $1,2 $ and $ 3.$ What is the possible grouping? I'll have either $\{(1,2,3)\}$ or $\{(1),(2),(3)\}$ or $\{(1,2),(3)\}$ or $\{1,(2,3)\}$ or $\{(2,(1,3)\}.$ So, I'll have $5$ possible grouping. In the same manner for $4$ objects, I'll have $14$ possible grouping. So, What about $n$ numbers and how could I formulate it?

Andrés E. Caicedo
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elnaz irannezhad
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    You are looking for Bell Numbers. Check this out http://en.wikipedia.org/wiki/Bell_number Also for $4$ it will be $15$ not $14$. – Anurag A Apr 16 '15 at 04:31
  • Thanks for useful hint, Andres; yes, It is the solution. Just wondering whether there is a code or pseudo-code for partitions or not – elnaz irannezhad Apr 16 '15 at 06:22

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