What is WA11?
P.S. subfactorial func is correct
P.P.S. Admins, is it possible there are some bugs here?

Edited by author 29.02.2016 01:26

The next formula is correct:
f(1) = 0;
f(n) = n*f(n-1) + (-1)^n;

But you need use long/big math (example: https://golang.org/pkg/math/big/)