Lemoine's conjecture

In number theory, Lemoine's conjecture, named after Émile Lemoine, also known as Levy's conjecture, after Hyman Levy, states that all odd integers greater than 5 can be represented as the sum of an odd prime number and an even semiprime.

History
The conjecture was posed by Émile Lemoine in 1895, but was erroneously attributed by MathWorld to Hyman Levy who pondered it in the 1960s.

A similar conjecture by Sun in 2008 states that all odd integers greater than 3 can be represented as the sum of a prime number and the product of two consecutive positive integers ( p+x(x+1) ).

Formal definition
To put it algebraically, 2n + 1 = p + 2q always has a solution in primes p and q (not necessarily distinct) for n > 2. The Lemoine conjecture is similar to but stronger than Goldbach's weak conjecture.

Example
For example, the odd integer 47 can be expressed as the sum of a prime and a semiprime in four different ways:
 * 47 = 13 + 2×17 = 37 + 2×5 = 41 + 2×3 = 43 + 2×2.

The number of ways this can be done is given by. Lemoine's conjecture is that this sequence contains no zeros after the first three.

Evidence
According to MathWorld, the conjecture has been verified by Corbitt up to 109. A blog post in June of 2019 additionally claimed to have verified the conjecture up to 1010.

A proof was claimed in 2017 by Agama and Gensel, but this was later found to be flawed.