function [ y ] = f_cx( x )
%F_CX Convex test function with minimum value zero, 
% input x a real vector with at least one component

const = 4; 
oc = 2*sqrt(const);

n = length(x);
y = 0;

for i = 1:n
   y = y + i^2*((exp(i*sum(x(1:i)))+const*exp(-i*sum(x(1:i))))-oc);
end



end


