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[数列] 数列通项

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大一新生 posted 2019-1-6 15:55 |Read mode
数列$\{a_n\}_{-\infty}^{+\infty}$每$10$个数字循环一次,当$n=1,2,\cdots,10$时,$a_n=n$.
求数列$\{a_n\}_{-\infty}^{+\infty}$的通项公式.(我用$mod$没写出来...)

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kuing posted 2019-1-6 16:22
每10个数字循环一次就是指周期为10是吗?如果是的话那就是 `a_n=(n-1)\bmod 10+1` 呗

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original poster 大一新生 posted 2019-1-6 19:15
回复 2# kuing
k版主,怎么写才能让下标为0和负整数时也适用哇?

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original poster 大一新生 posted 2019-1-6 19:24
不用分段的形式写似乎很难...

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kuing posted 2019-1-6 19:29
回复 3# 大一新生

2# 的通项也适用于0和负数啊,`(-1)\bmod10=9` 啊

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