# Combina

Combina-func

## Description

Minimum Origin Version Required: 2019 SR0

This function is used to calculate the number of **k**-combinations (with repetitions) from a given set with **n** elements, denoted by:

Please note that it counts the repetition as a possible combination, which is different from the Combine function. For example, in a set of 3 elements of "*a, b, c*", there are 3 combinations for 2 elements without repetitions (calculated by the Combine function): *ab, ac, bc*. But if take repetitions into account, there are 6 combinations (calculated by the Combina function): *aa, ab, ac, bb, bc, cc*.

## Syntax

double Combina(int n, int k)

## Parameters

**n**

- The number of elements in a given set. It must be a positive integer.

**k**

- The k-combinations. It must be a positive integer and
**k** < **n**.

## Return

Return the number of **k**-combinations (with repetitions) from a given set with **n** elements.

## Example

combina(4, 2) = ; // returns 10
Combina(8, 2) = ; // returns 36

## See Also

Combine, Permut, Permutationa