Goldbach's conjecture
Chen's theorem, another weakening of Goldbach's conjecture, proves that for all sufficiently large "n", formula_1 where "p" is prime and "q" is either prime or semiprime. In 2015, Tomohiro Yamada proved an explicit version of Chen's theorem: every even number greater than formula_2 is the sum of a prime and a product of at most two primes.