# Function stirlingS2 The Stirling numbers of the second kind, counts the number of ways to partition a set of n labelled objects into k nonempty unlabelled subsets. stirlingS2 only takes integer arguments. The following condition must be enforced: k <= n. If n = k or k = 1, then s(n,k) = 1 ## Syntax ```js math.stirlingS2(n, k) ``` ### Parameters Parameter | Type | Description --------- | ---- | ----------- `n` | Number | BigNumber | Total number of objects in the set `k` | Number | BigNumber | Number of objects in the subset ### Returns Type | Description ---- | ----------- Number | BigNumber | S(n,k) ## Examples ```js math.stirlingS2(5, 3) //returns 25 ``` ## See also [bellNumbers](bellNumbers.md)