13！/(2!2!2!2!）-4*12!/(2!2!2!）+6*11!/(2!2!)-4*10!/2!+9!

來源: AceOnRiver 於 2009-11-05 13:53:05 [] [舊帖] [給我悄悄話] 閱讀數 : (56 bytes)

same reasoning as 惡狼, slightly different coefficients.

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