Try something like that:
// power series dev using a loop
// value of e = 2.71828182846
#include <stdio.h>
int main()
{
int n, f;
float x;
float e;
x = 1.0;
f = 1;
e = 0.0;
//e = 1+x/1!+x2/2!+x3/3!+x4/4! ...
//e = 1 + x * x*2.0/2 + x*3.0/(2*3) + x*4.0/(2*3*4) ...
for ( n = 1; n < 11; n++ ) {
f *= n; // factorial, don't exceed 12!
e += x*n/f;
printf( "%f %d %d\n", e, n, f);
}
getchar(); // wait
return 0;
}