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# involution numbers list

Calculates the numbers of involutions of 0 through \e n objects.
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C++

## Involution Numbers List

 std::vectorinvolution_numbers_list( int n )
This function calculates the number of involutions for 0 through n objects, using the following recurrent sequence:



An involution is a permutation consisting only of fixed points and pairwise transpositions. It can be proven that to every involution there is a unique corresponding inverse.

### Example 1

#include <codecogs/maths/combinatorics/sequences/involution_numbers_list.h>
#include <iostream>
int main() {
std::vector<int> result = Maths::Combinatorics::Sequences::involution_numbers_list(10);
std::cout << "Number of values: " << result.size() << std::endl;
for (int i = 0; i < result.size(); i++)
std::cout << result[i] << "  ";
std::cout << std::endl;
return 0;
}
Output:
Number of values: 11
1  1  2  4  10  26  76  232  764  2620  9496

### References

SUBSET, a C++ library of combinatorial routines, http://www.csit.fsu.edu/~burkardt/cpp_src/subset/subset.html

### Returns

the involution numbers of order 0 to n

### Authors

Lucian Bentea (August 2005)
##### Source Code

Source code is available when you agree to a GP Licence or buy a Commercial Licence.

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