MatLab

x = [1 2 3 4 5 6 7 8 9 10];
x1 = x;
n = 4;
k = length(x);

for i = 1:k
    for j = 1:n-1
        x(i)= x(i)*x1(i);
    end
end

S = sum(x);
fprintf('Sum = %d\n', S);