This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A343973 #5 Jun 11 2023 14:22:27
%S A343973 2,3,5,7,11,13,23,47,193,383
%N A343973 Primes p such that both p-1 and p+1 are in A093641.
%C A343973 Primes p such that p-1 and p+1 each have at most one odd prime factor (counted with multiplicity).
%C A343973 Terms > 3 must be either of the form 3*2^k+1 with 3*2^(k-1)+1 prime, or of the form 3*2^k-1 with 3*2^(k-1)-1 prime.
%C A343973 There are no more terms up to 3*2^5000+1.
%C A343973 Conjecture: these are all the terms.
%e A343973 a(5) = 11 is a term because 11-1=5*2^1 and 11+1=3*2^2 with 11, 5 and 3 prime.
%p A343973 {3,7} union select(t -> isprime(t) and isprime((t+1)/2), {seq(3*2^k+1,k=1..3000)})
%p A343973 union select(t -> isprime(t) and isprime((t-1)/2), {seq(3*2^k-1,k=1..3000)});
%Y A343973 Cf. A093641.
%K A343973 nonn,more
%O A343973 1,1
%A A343973 _J. M. Bergot_ and _Robert Israel_, May 05 2021