http://jijixi.azito.com/cgi-bin/diary/index.rb?date=20060711#p02 経由で、 http://ll.jus.or.jp/2006/blog/doukaku2 class Collatz include Enumerable def initialize( n ) @n=n @cache={1=>1} end def calc(n) @cache[n]=_calc(n) unless @cache.inclu…