A077435 - OEIS

#include<stdio.h>
#include<stdlib.h>

#define min(a,b) ((a)<(b)?(a):(b))

int GCD(int a, int b)
{
    do{
        if(a>b) {a^=b^=a^=b;}
    } while(b%=a);
    return a;
}

int f(int n, int a, int b)
{
    int result = 0, i, j;
    result = (n-1)*(n-1);
    for (j=1; j<=n-b; j++)
        for (i=1; i<=n-a; i++)
            if (GCD(i, j)==1)
                result += (min((n-a)/i,(n-b)/j)+min((a-1)/i,(b-1)/j)) * (min((n-b)/i,(a-1)/j)+min((b-1)/i,(n-a)/j));
    return result;
}

int F(int n)
{
    int result = 0, tmp = 0, a, b;
    if (n==1)
        return 1;
    if (n%2)
    {
        for (a=1; a<=(n-1)/2; a++)
            result += f(n, a, a);
        for (b=1; b<=(n-1)/2; b++)
            tmp += f(n, (n+1)/2, b);
        result = 4*(result+tmp);
        tmp = 0;
        for (b=1; b<=(n-3)/2; b++)
            for (a=b+1; a<=(n-1)/2; a++)
                tmp += f(n, a, b);
        result += 8*tmp + f(n, (n+1)/2, (n+1)/2);
    }
    else
    {
        for (a=1; a<=n/2; a++)
            result += f(n, a, a);
        for (b=1; b<=(n-1)/2; b++)
            for (a=b+1; a<=n/2; a++)
                tmp += f(n, a, b);
        result = 4*result + 8*tmp;
    }
    return result;
}

int main(void)
{
    int n, N=20;
    for (n=1; n<N; n++)
    {
        printf("%d,%d\n", n, F(n));
    }
    system("pause");
    return 0;
}