21i hope empty circles are not taken into consideration!!? :D
can u tell the answer if u have ?
106no .. empty circles are not taken into consideration (atleast 1 person in a circle)
and i dont have the answer.
This was a question our recently concluded technical - interhostel event
341I guess Stirling numbers of the first kind is what you need
http://en.wikipedia.org/wiki/Stirling_numbers_of_the_first_kind
66Yes I think the required number should be
\sum_{k=1}^n \left[\begin{array}{c}n \\ k \end{array}\right]
where \left[\begin{array}{c}n \\ k \end{array}\right] denotes the unsigned Stirling number of the first kind which counts the number of permutations of n elements with k disjoint cycles.