Any even number not less than 6 can be expressed as the sum of two odd prime numbers; b)

Any odd number not less than 9 can be expressed as the sum of three odd prime numbers. Euler also proposed another equivalent version. In other words, any even number greater than 2 can be written as the sum of two prime numbers. Euler's proposition is more demanding than Goldbach's. Now these two propositions are generally called Goldbach conjecture. The proposition that any big even number can be expressed as the sum of a number not exceeding one prime factor and another number not exceeding b prime factors is "a+b". Coriolis conjecture is to prove that "1+ 1" holds. 1966 Chen Jingrun proved that "1+2" holds, that is, "any big even number can be expressed as the sum of a prime number and another prime number factor not exceeding 2".