排列組合，定義“好字”為由三個字母A、B、C所組成的序列
定義一個“好字”為由三個字母[i]A[/i]、[i]B[/i]、[i]C[/i]所組成的序列（[i]A[/i]、[i]B[/i]、[i]C[/i]不必全部出現在序列中），其中[i]A[/i]不能緊接在[i]B[/i]之後，[i]B[/i]不能緊接在[i]C[/i]之後且[i]C[/i]不能緊接在[i]A[/i]之後。求六個字母的“好字”共有____個。 第一字方法 為 3第二字方法 為 2
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第六字方法 為 2
\( 3 \cdot 2 \cdot 2 \cdot 2 \cdot 2 \cdot 2 =96 \) 幫忙補上出處
Define a good word as a sequence of letters that consists only of the letters A,B and C _ some of these letters may not appear in the sequence _ and in which A is never immediately followed by B, B is never immediately followed by C, and C is never immediately followed by A. How many seven-letter good words are there?
(2003AIME，[url=http://www.artofproblemsolving.com/Forum/resources.php?c=182&cid=45&year=2003]http://www.artofproblemsolving.c ... 82&cid=45&year=2003[/url])
這裡可以下載2003AIME中文版題目
[url=http://forum.nta.org.tw/examservice/showthread.php?t=52834]http://forum.nta.org.tw/examservice/showthread.php?t=52834[/url]
[url=http://forum.nta.org.tw/examservice/showpost.php?p=229485&postcount=5]http://forum.nta.org.tw/examserv ... =229485&postcount=5[/url]
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