function HW3_1(N) x = 1:N; y = zeros(1,N); for n = 1:N for i = 1:n y(n) = y(n) + 1/(i^2); end end exa = pi^2/6; y = abs( y - exa ); loglog(x,y); end % Result: a straight line as expeced en ~ O(1/n)