Talk:Special factorials
Reverse factorial algorithm
I took a stab at translating the reverse factorial algorithm used in the Factor entry to Java. It should be almost as efficient as taking the factorial itself. <lang java>public static int rf(int n) {
int a = 1; int b = 1; while (n > a) { b++; a = a * b; } if (a == n) return b; else return -1; //undefined }</lang>
Why is af(0) 0?
Is it that 0 is the additive identity the way that factorial of 0 is 1 is the multiplicative identity? If so why should it be the identity anyway?
- I think it's just that the formula literally produces 0 for n = 0.
First run through, k is 1, this produces -1. Second run through, k is 0, this produces 1 and their sum is 0. --Chunes (talk) 17:36, 16 March 2021 (UTC)