Pandasで連番値をカウント

https://qiita.com/Masutani/items/3cea640da7d1f5f58af1

https://ja.stackoverflow.com/questions/69962/pandas%E3%81%A7-%E9%A3%9B%E3%81%B3%E9%A3%9B%E3%81%B3%E3%81%AE%E5%88%97%E7%95%AA%E5%8F%B7%E3%82%92%E9%80%A3%E7%95%AA%E3%81%AB%E3%81%97%E3%81%9F%E3%81%84

https://teratail.com/questions/293803