Virgil wrote: > In article <email@example.com>, > jim <firstname.lastname@example.org> wrote: > >> Is there any way to combine 2 primes to get a larger prime, either >> guarantying the primality of the result or with a quick test for the >> primality? >> >> Thanks, >> Jim > > The only time that the sum of two primes is also a prime is when their > difference is 2 in such "twin primes" as 5 and 7 or 17 and 19 or 41 and > 43. > > http://en.wikipedia.org/wiki/Twin_prime
Leaving aside the prime 2, the sum of two primes is even and thus divisible by two. Clearly I'm missing something.
-- Nam Nguyen in sci.logic in the thread 'Q on incompleteness proof' on 16/07/2013 at 02:16: "there can be such a group where informally it's impossible to know the truth value of the abelian expression Axy[x + y = y + x]".