在一个十进制正整数中,如果它含有偶数(包括零)个数字 8 ,则称它为“优数” ,否则就称它为“非优数” .那么,长度(位数)不超过
(
是正整数)的所有“优数” 的个数是 __________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
2018高三·全国·竞赛 查看更多[1]
更新时间:2018-12-17 10:11:32
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