Stirling numbers of the first kind
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The Stirling numbers of the first kind s(n, k) count the number of ways to permute a list of n items into k cycles.For example, the list {1, 2, 3, 4} can be permuted into two cycles in the following ways:
There are 11 such permutations, thus s(4, 2) = 11.
- {{1,3,2},{4}}
- {{1,2,3},{4}}
- {{1,4,2},{3}}
- {{1,2,4},{3}}
- {{1,2},{3,4}}
- {{1,4,3},{2}}
- {{1,3,4},{2}}
- {{1,3},{2,4}}
- {{1,4},{2,3}}
- {{1},{2,4,3}}
- {{1},{2,3,4}}
Here are some illegible diagrams showing the cycles for permutations of a list with five elements.
s(5, 1) = 24:
s(5, 2) = 50:
s(5, 3) = 35:
s(5, 4) = 10:
s(5, 5) = 1:
Designed and rendered using Mathematica 3.0 for NeXT.
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