發送短信 : On particular solutions of linear difference equations with constant coefficients

  _____    _    _     _  _    _    _    __   _   
 / ____|| | || | ||  | \| || | || | || | || | || 
/ //---`' | || | ||  |  ' || | || | || | '--' || 
\ \\___   | \\_/ ||  | .  || | \\_/ || | .--. || 
 \_____||  \____//   |_|\_||  \____//  |_|| |_|| 
  `----`    `---`    `-` -`    `---`   `-`  `-`