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edited Mar 26, 2017 at 23:45

MATLAB, 33 bytes

@(n)(-1)^n*hypergeom([1 -n],[],1)

UsesAnonympus function that uses the formula in Section 3 of Derangements and applications by Mehdi Hassani.

Example use:

>> @(n)(-1)^n*hypergeom([1 -n],[],1) ans = @(n)(-1)^n*hypergeom([1,-n],[],1) >> ans(6) ans = 265

@(n)(-1)^n*hypergeom([1 -n],[],1)

Uses the formula in Section 3 of Derangements and applications by Mehdi Hassani.

Example use:

>> @(n)(-1)^n*hypergeom([1 -n],[],1) ans = @(n)(-1)^n*hypergeom([1,-n],[],1) >> ans(6) ans = 265

@(n)(-1)^n*hypergeom([1 -n],[],1)

Anonympus function that uses the formula in Section 3 of Derangements and applications by Mehdi Hassani.

Example use:

>> @(n)(-1)^n*hypergeom([1 -n],[],1) ans = @(n)(-1)^n*hypergeom([1,-n],[],1) >> ans(6) ans = 265

answered Mar 26, 2017 at 23:36

@(n)(-1)^n*hypergeom([1 -n],[],1)

Uses the formula in Section 3 of Derangements and applications by Mehdi Hassani.

Example use:

>> @(n)(-1)^n*hypergeom([1 -n],[],1) ans = @(n)(-1)^n*hypergeom([1,-n],[],1) >> ans(6) ans = 265