function w=well(u)
%
%  function w= well(u)
%
%  Theis's well function
%
Econst = 0.577215664901532860606512;

n = 10;
term = 1;
for k = n:-1:2  
   term =  1 + ((1-k)/k^2)*u.*term;
end
w = -Econst - log(u) + u.*term;

