%
function [A,b] = poisson2(n)  
%
h = 1/(n+1);
A = full(gallery('poisson',n));
x = linspace(h,1-h,n);
y = 0;
for j=1:n
  y = y+h;
  first = (j-1)*n + 1;
  last  = j*n;
  b(first:last) = 5*sin(2*pi*x)*sin(pi*y);
end
b = (pi*h)^2*b';

