Definition:Stirling Numbers of the First Kind/Unsigned/Definition 1
Definition
Unsigned Stirling numbers of the first kind are defined recursively by:
- $\ds {n \brack k} := \begin{cases}
\delta_{n k} & : k = 0 \text { or } n = 0 \\ & \\ \ds {n - 1 \brack k - 1} + \paren {n - 1} {n - 1 \brack k} & : \text{otherwise} \\ \end{cases}$
where:
- $\delta_{n k}$ is the Kronecker delta
- $n$ and $k$ are non-negative integers.
Notation
The notation $\ds {n \brack k}$ for the unsigned Stirling numbers of the first kind is that proposed by Jovan Karamata and publicised by Donald E. Knuth.
The notation $\map s {n, k}$ for the signed Stirling numbers of the first kind is similar to variants of that sometimes given for the unsigned.
Usage is inconsistent in the literature.
Also see
Source of Name
This entry was named for James Stirling.
Technical Note
The $\LaTeX$ code for \(\ds {n \brack k}\) is \ds {n \brack k}
.
The braces around the n \brack k
are important.
The \ds
is needed to create the symbol in its proper house display style.
Sources
- 1997: Donald E. Knuth: The Art of Computer Programming: Volume 1: Fundamental Algorithms (3rd ed.) ... (previous) ... (next): $\S 1.2.6$: Binomial Coefficients: $(46)$