function [p, A] = stop13(rolls)
  if nargin < 1
    rolls = 11;
  elseif rolls > 11
    rolls = 11;
  end

  A = toeplitz(zeros(17,1),[0 ones(1,6)/6 zeros(1,10)]);
  A(1:6,1:6) = eye(6);

  p = A^rolls * [zeros(16,1); 1];
end