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[组合] $a_i$是八位数$A$中数码$i$的数量,求$A$

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abababa posted 2019-8-4 20:39 |Read mode
设首位非零的八位数$A=\overline{a_0a_1 \cdots a_7}$,其中$a_i$是$A$中数码$i$的数量,问$A$是多少。

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kuing posted 2019-8-4 22:09
2010 年出过五个数的(《撸题集》P.803),而且问的也比较简单,这个八个数还要确定具体的值,挺麻烦。

首先还是有
\[a_0+a_1+a_2+\cdots+a_7=0a_0+1a_1+2a_2+\cdots+7a_7=8,\]然后懒得慢慢推理了,扔给MMC(A)算,符合上述等式的解只有若干组,一一检验吧……

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