I knew this problem in a WeChat group chat. It is said to be a problem for primary-school students. Here is the problem. How many integers with all digits being just 1,2 or 3 and the sum of all digits being 10? For example, 12331 and 22222. We could ask a more general qu ...
昨天晚上设了闹钟，凌晨02:30，因为这个时候金星才从东方升起。 凌晨2点半，闹钟准时响起，脑袋还有点不清醒。拿起眼镜和手机，迅速跑上天台。唿，凉爽！瞬间清醒。 金星如约而至，比我想象中小，就在月亮下方。周围有御夫座，双子座，猎户座，白羊座和金牛座。下面的图片都是我用手机拍出来的，也有Star Wa ...
Fang and I found enhanced inequalities about the arithmetic mean and the geomertic mean of n positive numbers (see this arXiv entry for details). Ofcourse it is impossible to improve those classic inequalities without new information. Let me explain our ideas. Suppose we k ...
I took photos of Moon last night with my iphone 6s. 10 of them are stacked to produce the final picture below. Indeed it is better than single ones. This is the first time that I use registax to stack pictures. Interestingly, I found a question mark ? on Moon. ...
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