/*
 * Calculate Basel sum \sum_{i=1}^{\infty} \frac{1}{i*i}
 * repeated calculations.
 */

#include <stdio.h>
#include <math.h>

#define N 10000
#define M 19

int main(void) {
    long i, j, n;
    double s, ans;
    
    ans =  M_PI*M_PI/6;
    n = N;

    for (j = 0; j < M; j++) {
        s = 0.;

        for (i = 1; i <= n; i++) {
            s += 1./((double) i*i);
        }
    
        printf("%10ld   %20.14f    %20.14f     %20.14f\n", n, s, ans, ans-s);
        n *= 2;
    }
    return(0);
}