# Scientific Calculator

##
bthiessen/subfactorial

By bthiessen

Subfactorial: (derangement) permutation of the elements of a set, such that no element appears in its original position

Tagged:

```
subfactorial = function(n) {
var x = 1;
if (n == 1) -> x=0;
if (n < 0) -> x="Error: argument must be a non-negative integer";
if (n > 1) -> (
var a = 1;
var sign = -1;
x = n!;
while (a <= n) -> (
x += sign * (n!/a!);
a += 1;
sign = sign * -1;
);
);
x;
}
```

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