{n\brace k} - LaTeX Symbol

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{k n}

{n\brace k}

The notation {n\brace k} represents a Stirling number of the second kind, which counts the number of ways to partition a set of n objects into k non-empty subsets.

Examples

{2 5} = 15

The number of ways to partition a set of 5 objects into 2 non-empty subsets.

{5\brace 2} = 15

{3 4} = 6

The number of ways to partition a set of 4 objects into 3 non-empty subsets.

{4\brace 3} = 6

{1 6} = 1

The number of ways to partition a set of 6 objects into 1 non-empty subset, which is just the set itself.

{6\brace 1} = 1