# Quod Erat Demonstrandum

## 2017/05/27

### 帕斯卡三角形某結果

Filed under: Fun,Pure Mathematics — johnmayhk @ 8:56 上午
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## 2016/02/28

### 冪和表成二項式係數

Filed under: Fun,NSS,Pure Mathematics — johnmayhk @ 12:05 上午
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2016-01-30 在圖書館某小書的某附錄，見

https://en.wikipedia.org/wiki/Faulhaber%27s_formula

## 2016/02/20

### nHk

Filed under: NSS — johnmayhk @ 8:33 上午
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$\displaystyle \sum^n_{k=0}H^n_k=H^{n+1}_n$

## 2016/01/25

### (a+b) 的 4 次

Filed under: Fun — johnmayhk @ 3:29 下午
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## 2015/02/03

### 玩 nCr

Filed under: Fun,NSS — johnmayhk @ 3:30 下午
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$C^{m+n}_2=C^m_2+C^n_2+mn$

$C^n_r=\frac{n!}{r!(n-r)!}$

## 2014/02/11

### 二項極限

Filed under: NSS,Pure Mathematics — johnmayhk @ 3:16 下午
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（圖片來源：Mathematics）

“…is a recently discovered beauty, probably in 2012…"

## 2014/02/03

### 卡塔蘭

Filed under: Fun,NSS — johnmayhk @ 1:11 上午
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1,1,2,5,14,42,…

## 2008/11/21

### Exist or does not exist

Is giving hints a good way to help students in solving mathematics problems? Urm, sometimes it may not.

Here is a common m.i. question in recent F.4 additional mathematics regular test:

Show that $n^3 - n + 3^n$ is divisible by 3 for any positive integer $n$. (more…)

## 2008/10/17

### 不能秒殺的提問

1. 誰發明 $_nC_r$ 這個符號？
2. 畢氏數組中是否必然存在 3 或 5 的倍數？ (more…)