In 2016, Du Kien Xuan shocked the world's mathematics community when he found a simple way to verify pseudoprime numbers (Carmichael numbers). Before that, there were many methods to determine prime and pseudoprime numbers but they were difficult to implement. The fact that a person with no formal mathematics training, only a secondary school degree, found a new method to solve the mathematical problem of the century, made everyone curious.

Yu Jianchun was born in 1983 in a poor farming family in Henan (China). Poverty made his family want him to go out and earn money early. After graduating from high school, his parents enrolled him in Zhengzhou Veterinary College (China) to study Animal Husbandry. They hoped that after graduating, he would return to his hometown to raise animals to improve his family's economy . Helpless in the face of his family's circumstances, he accepted.

In his free time, he went to the school library to read books. By chance, he found a book called Mathematical Conjectures . In it, the problem of pseudo-prime numbers attracted him. However, because he had no formal training in Mathematics, he encountered many difficulties when researching and reading documents.

Yu Jianchun presents a method for determining pseudoprime numbers at Zhejiang University on June 14, 2016. Photo: Baidu

After graduating, he did not return to his hometown because he wanted to spend time in the city doing research. With only a high school diploma and lacking social skills, he had to work as a factory worker. In the first years of working, because of his passion for research, he could not focus on his work and was often fired.

Many people around him even mocked him harshly. Despite everyone's doubts, he still immersed himself in the world of Mathematics. He believed that with a certain amount of effort, he would succeed. In 2008, the new algorithm to determine pseudo-prime numbers researched by Kien Xuan had results.

At this time, to evaluate his research, he wrote letters to many universities at home and abroad. For 8 years, with great expectations, he received no response. He quit his job and went to many cities in China to find professors but could not find them. They said that he had no research experience and that the results would not lead anywhere.

With his finances exhausted, he made a last ditch effort by writing directly to Mathematician Cai Tianjin. On June 14, 2016, Professor Tan invited him to Zhejiang University to present his research with the participation of many Mathematicians.

According to Sohu , after more than 2 hours of presentation, the attendees were all surprised to admit that his method was more effective than the traditional one. "Kien Xuan has not been formally trained in Number Theory nor has he studied advanced Mathematics. Therefore, this result comes from his talent and sensitivity to numbers," Professor Tan commented.

He was highly appreciated by mathematician William Banks, who also studied the problem. Sharing with CNN , the professor said: "The construction of a solution to find pseudo-prime numbers was done by many scholars more than 20 years ago. Including the additional results of me and other authors, the research has only identified 1 variation on the same topic. Meanwhile, Kien Xuan's method can be applied to 4 different complex mathematical problems."

The above achievements helped Kien Xuan to be sought after by the Mathematics community. Many professors at home and abroad sent him invitations to cooperate, but he refused, fearing that he was not qualified enough: "Maybe I am sensitive to numbers and spend more time on research than others, but I lack formal knowledge of Algebra and Geometry."

Even at that time, schools were willing to sponsor his studies, but he refused: "At the age of 33, I cannot study for many more years. I want to get married before thinking about research." At that time, he joined a company with a high salary. However, later, due to work pressure, he quit to work as a factory worker until now, with a salary of 8,000 NDT/month (about 28.4 million VND).

In a recent interview, at the age of over 40, when asked why he had refused previous development opportunities, he explained: "Perhaps it was the influence of my family, someone from a poor background like me just wanted to find a job to make money quickly. Sometimes I wonder if life would be different if I had chosen to continue studying or pursue research. However, when looking back at my current job, I wish for nothing more than a peaceful life."

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