I met a problem recently which need to prove the below conclusion.
There is a example that $$$n=13,p=5,2p+1=11$$$ meet this constraint
I wrote something and check it's correct when $$$40\le n\le 10^5$$$ but is there any complete proof for such B exists?
I've learnt Bertrand-Chebyshev Theorem that there exists a prime $$$p\in[n,2n]$$$ and it may help.
Thank you.