Goldbach is a German middle school teacher and a famous mathematician. He was born in 1690, and was elected as an academician of Russian Academy of Sciences in 1725. 1742, Goldbach found in his teaching that every even number not less than 6 is the sum of two prime numbers (numbers that can only be divisible by 1 and itself). For example, 6 = 3+3, 12 = 5+7 and so on. 1On June 7th, 742, Goldbach wrote to Euler, a great mathematician at that time, and put forward the following conjectures: (a) Any even number ≥6 can be expressed as the sum of two prime numbers. (b) Any odd number ≥9 can be expressed as the sum of no more than three prime numbers. This is the famous Goldbach conjecture. In his reply to him on June 30th, Euler said that he thought this conjecture was correct, but he could not prove it. Describing such a simple problem, even a top mathematician like Euler can't prove it. This conjecture has attracted the attention of many mathematicians. Since Goldbach put forward this conjecture, many mathematicians have been trying to conquer it, but they have not succeeded. Of course, some people have done some specific verification work, such as: 6 = 3+3, 8 = 3+5, 10 = 5+5 = 3+7, 12 = 5+7,14 = 7+7 = 3+/kloc. Someone checked the even numbers within the 8th power of 33× 10 and greater than 6, and Goldbach conjecture (a) was established. But strict mathematical proof requires the efforts of mathematicians. Since then, this famous mathematical problem has attracted the attention of thousands of mathematicians all over the world. 200 years have passed and no one has proved it. Goldbach conjecture has therefore become an unattainable "pearl" in the crown of mathematics. People's enthusiasm for Goldbach conjecture lasted for more than 200 years. Many mathematicians in the world try their best, but they still can't figure it out.

"1+S" and Chen Theorem

It was not until the 1920s that people began to approach it. 1920, the Norwegian mathematician Brown proved by an ancient screening method, and reached a conclusion that every even number with a large ratio can be expressed as (9+9). This method of narrowing the encirclement is very effective, so scientists gradually reduce the prime factor in each number from (99) until each number is a prime number, thus proving Goldbach's conjecture. At present, the best result is proved by China mathematician Chen Jingrun in 1966, which is called Chen Theorem: "Any large enough even number is the sum of a prime number and a natural number, while the latter is only the product of two prime numbers." This result is often called a big even number and can be expressed as "1+2". Before Chen Jingrun, the progress of even numbers can be expressed as the sum of the products of S prime numbers and T prime numbers (referred to as "s+t" problem) as follows: 1920, Norwegian Brown proved "9+9". 1924, Latmach of Germany proved "7+7". 1932, Esterman of England proved "6+6". 1937, Lacey in Italy successively proved "5+7", "4+9", "3+ 15" and "2+366". 1938, Bukit Tiber of the Soviet Union proved "5+5". 1940, Bukit Tiber of the Soviet Union proved "4+4". 1948, Rini of the Hungarian Empire proved "1+C", where c is an infinite integer. 1956, Wang Yuan of China proved "3+4". 1957, Wang Yuan of China proved "3+3" and "2+3". 1962, Pan Chengdong of China and Barba of the Soviet Union proved "1+5", and Wang Yuan of China proved "1+4". 1965, Buchwitz Taber and vinogradov Jr. of the Soviet Union and Pemberley of Italy proved "1+3". 1966, China Chen Jingrun proved "1+2". It took 46 years from Brown's proof of 1920 of "9+9" to Chen Jingrun's capture of 1966 of "+2". Since the birth of Chen Theorem for 30 years, it is futile for people to further study Goldbach conjecture.