In this paper, we investigate the convolution sums Sigma((a+b+c)x=n) a, Sigma(ax+by=n) ab, Sigma((ax+by+cz)x=n) abc, Sigma((ax+by+cz+du)x=n) abcd, where a, b, c, d, x, y, z, u, n is an element of N. Many new equalities ...