>>323
あった。thx
https://books.google.co.jp/books?id=gAPqBwAAQBAJ&;pg=PA67&lpg=PA67&dq=contemplate+the+second+order+difference+equation&source=bl&ots=sWOAD9FkYq&sig=6ciWUQi6ZWeVSU5zY2eaK5JyPV4
&hl=ja&sa=X&ved=2ahUKEwjD_oTP8NfdAhU1HjQIHSEoAmEQ6AEwDHoECEkQAQ#v=onepage&q=contemplate%20the%20second%20order%20difference%20equation&f=false