Over the weekend, Han Sen and Qin Jing officially moved into their new home, a villa in the Jiuzhang Villa, which is far away from the school, but the life of a beautiful small single-family villa is still very desirable.

Han Sen didn't have too many friends in Yanjing, because he studied abroad all the year round, Han Sen didn't actually have too many friends, and when he moved to a new home, only Qin Jing's parents, Han Sen's students, and a few of Qin Jing's close friends in the hospital came.

Zhang Bin likes the house type of Han Sen's house, and the environment here is also good, so he asked, "Teacher, the new home is so great!" Are there any houses for sale in this community? I'd like to buy a set too! ”

Han Sen smiled and said, "You Zhang Sanfu still have things that you can't buy!" ”

Behind Zhang Bin was Zhuang Wen, who was young and holding a simple gift and said with a smile: "Teacher, congratulations on the housewarming!" ”

"Oh, that's so polite, and there's a gift!" Han Sen smiled and accepted Zhuang Wen's gift.

Then there were several young doctors from Union Hospital, who respectfully spoke to Han Sen: "Hello Academician Han! ”

"Hello Academician Han!"

Han Sen hurriedly greeted him enthusiastically: "Hello, hello, please come in!" ”

In the kitchen, Qin Jing with an apron was busy with his mother, there were not too many people, and the reception was a family banquet, and a group of little doctors immediately ran to the kitchen to help.

The remaining men sat in front of the coffee table, drinking tea, discussing the interesting story of Han Sen's parents' global travel, Han Sen's parents have now become Internet celebrity anchors on Douyin, and the first to benefit from the improvement of Han Sen's influence in the world is the two of them.

A dinner ceremony, witnessed by several relatives and friends, Han Sen and Qin Jing officially became the co-owners of the family.

Now, Qin Jing and Han Sen have a lot of real estate: Qin Jing of Wanliu Academy has a set in his name, Ludong Han Zuodong has a wedding house for Han Sen and Qin Jing, and Hanzhuang Village has planned a big homestead for Han Sen, and here is another set.

......

In the new house, Qin Jing, who was like a fan of small wealth, was very happy to count their family property.

In the study, Han Sen read a research paper handed to him by Qin Lan: "If p is a prime number, if p is not divisible by a, then a^(p-1)≡1 (mod p), and if p is divisible by a, then a^(p-1)≡0 (mod p)......"

Han Sen could see at a glance that this was a study related to "pseudoprime",

A pseudoprime number, also known as a pseudoprime number, satisfies Fermat's small theorem, but it is not a prime number in itself. The smallest pseudoprime number is 341. It has been proven that the number of pseudoprimes is infinite.

In fact, Fermat's theorem gives necessary but not sufficient conditions for determining prime numbers. If n is divisible by 2^(n-1)-1, and n is a non-even composite number, then n is a pseudoprime. The first pseudoprime number 341 was discovered by Sarrus in 1819.

Fermat's minor theorem means that if a number p satisfies gcd(a, p) = 1 and a^(p-1)≡0 (mod p), then p is prime. But there is a special case, which means that Fermat's small theorem is buggy, but the same cannot be said. Fermat's minor theorem can only be pushed forward, not backward. So p satisfies Fermat's theorem, but p is not a prime number, but another pseudoprime number.

This research direction is still good.

His mentor Han Sen has made great achievements in number theory, and Qin Lan also chose this research direction

Looking at Qin Jing who came in, Han Sen handed out Qin Lan's paper and commented: "This kid is more powerful than I imagined." ”

Qin Jing walked behind Han Sen, helped Han Sen pinch his shoulder, glanced at his brother's name, and said proudly: "That's, don't look at whose brother it is." ”

Han Sen smiled and said, "Hehe, the sound insulation effect of this new home should be quite good!" ”

Because there is a doctoral interview tomorrow, Han Sen closed Qin Lan's thesis and picked up his little Qin Jing, young man, you still have to sleep.

......

The new Monday is so far away from the next weekend, it is always an unpleasant day, even in Tsinghua University, the top students here are in a bad mood on Monday, and they start a new week of study with their schoolbags on their backs.

With the strengthening of the influence of the "Han Sen School" in the field of international economics and the academic influence of the Journal of Tsinghua University, Tsinghua University has risen violently in the new global university rankings, and its neighbor Peking University has been thrown far away, but this also makes the top students of the entire Tsinghua University feel pressure, and they can't embarrass the school.

Han Sen's Bentley drove into the PBC School of Finance amid the admiring gaze of the students on campus.

Entering his office, Zhang Bin, Zhuang Wen and Qin Lan were already here, and Han Sen said to Qin Lan: "I have read your paper, it is not bad." ”

Number theory, this thing is very magical, his research threshold is not high, and basically a little mathematical foundation can be understood, which has led to a lot of research on number theory.

Of course, Han Sen's research on number theory has stood at the top of the world, which has led to countless letters about number theory problems sent to Han Sen's office every day, and some mathematicians from all over the world come to Han Sen to discuss number theory problems, and it is Qin Lan who helps Han Sen deal with these letters.

The "flash of inspiration" again and again combined with Qin Lan's solid foundation, so he completed this paper.

However, Han Sen's focus today is not Qin Lan's thesis, he is going to interview two doctoral students today, and he said to Qin Lan: "Go to dinner at home in the evening, and we will talk about your thesis later." ”

In the office, Zhuang Wen, who was pretending to be serious about his work, was a little jealous when he looked at Han Sen and Qin Lan's closeness.

Then Zhuang Wen heard Han Sen say to him: "Zhuang Wen, you are here too!" ”

Zhuang Wen nodded happily.

Sitting in his place, it was very good, the thermos cup had been filled with hot water, Han Sen asked Zhang Bin, "Zhang Bin, are Yao Ruzhi and Kuang Tong here?" ”

Zhang Bin opened his mouth and replied: "Here, I arranged it in the office of the Department of Mathematics. ”

Han Sen picked up the water cup on his desk and said to the three students: "Let's go, you guys also go over together, and see your senior brothers in the future." ”

.......

In the office building of the Department of Mathematics of Tsinghua University, in an office with a nameplate marked "Academician Han Sen's Office", Yao Ruzhi and Kuang Tong, dressed in neat suits, sat here.

Yao Ruzhi opened his mouth and introduced: "Hello, my name is Yao Ruzhi. ”

Kuang Tong held Yao Ruzhi's hand and said with a smile: "Hello, my name is Kuang Tong, you look very young." ”

Geniuses are inevitably proud, Yao Ruzhi said with a smile with a little pride: "Twenty-five, Princeton University has just graduated from graduate school in mathematics"

"Math?" Kuang Tong was stunned, and subconsciously thought that Yao Ruzhi was a mathematics major who switched to economics.

Yao Ruzhi spoke: "Well, Academician Han Sen agreed to give me a place as a doctoral student in mathematics. ”

Hearing that Han Sen had specially prepared a place for this young man for a doctorate in mathematics, Kuang Tong was shocked and said, "Amazing! My name is Kuang Tong, I am 28 years old, and I was a graduate student at PBC School of Finance, and I worked for two years. ”

"Fortunately, fortunately."