n=20;
A=zeros(n);

A(1,:)=[2:2:2*n];

% A(:,1)=2*n*sin(10*[1:n]/pi/n)';

A(n,:)=[2*n:-2:2];

surf(A);
shading interp;
pause;
for i=1:300
   for j=2:n-1
      for k=2:n-1
         A(j,k)=(A(j+1,k)+A(j-1,k)+A(j,k+1)+A(j,k-1))/4;
      end
   end
   if mod(i,4)==0 
      pause;
      surf(A); shading interp;
   end
end
surf(A);