Hi! I need to change the equation in this function!

Hi! I need help with this function. I need to change the equation of Leibniz (pi/4=(1-1/3+1/5-1/7+1/9...-) to this one (pi/2= 2/1 2/3*4/3*4/5*6/5...) [Wellis Product]. The objective to the function is the following: Implement the Wellis' equation in a function that receives the relative error willing to accept and return the user a vector with all values of π and other vector estimated with relative errors associated with each value of π. The function is done with the Leibniz, but I dont know how to change it with the Wellis equation because a multiplication. The function that I have is the following (The function is in arrays): Thanks a lot!

function [ES,ER]=pi2array(x)  
%ES is the array of estimated values of pi and ER is the error associated with each value of pi
RT=pi;
ter=0;
estimado=1;
er=2*x;
ER = [] ;
ES = [];
while er>=x
  z=((1^(ter)+(ter+1))/(ter+1))^((-1)^ter);
  estimado=(estimado*z);
  es=estimado* 2;
  er=100*abs((es-RT)/RT);
  ter=ter+1;
  ES(ter) = es ;
  ER(ter) = er ;
end
end