/* http://t...content-available-to-author-only...h.net/test/read.cgi/tech/1339338438/415 */
 
#include <stdio.h>
#include <stdlib.h>
 
int X(int n)
{
    if (n < 1)
        return 0;
    return 2 * X(n - 1) + 1;
}
 
int main(int argc, char *argv[])
{
    int i;
    if (argc == 1)
        printf("X(0) = %d\n", X(0));
    else
        for (i = 1; i < argc; i++) {
            int n = atoi(argv[i]);
            printf("X(%d) = %d\n", n, X(n));
        }
    return 0;
}

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