Here is a related link

來源: yma16 於 2009-11-29 13:30:03 [] [博客] [舊帖] [給我悄悄話] 閱讀數 : (237 bytes)

http://web.wenxuecity.com/BBSView_archives.php?SubID=netiq&MsgID=118341&yr=2007

The link says it should have a limit. I estimated it for a few steps, it seems it >2. I think you need many more steps if you want it be close to 4.

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