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 A175172 #20 Apr 12 2025 02:14:17 %S A175172 2,5,41,353 %N A175172 Primes p such that 3*2^p+1 is also prime. %C A175172 If it exists, a(5) > 250000. - _Hugo Pfoertner_, Apr 12 2025 %F A175172 A000040 INTERSECT A002253. - _R. J. Mathar_, Jan 04 2011 %e A175172 For p=2, 3*2^2+1=13; p=5. 3*2^5+1=97; p=41, 3*2^41+1=6597069766657. %p A175172 select(p->isprime(p) and isprime(3*2^p+1),[$0..5000]); # _Muniru A Asiru_, Dec 19 2018 %t A175172 Select[Prime[Range[1000]], PrimeQ[3 2^# + 1] &] (* _Vincenzo Librandi_, Dec 19 2018 *) %o A175172 (Magma) [p: p in PrimesUpTo(4000) | IsPrime(3*2^p+1)]; %Y A175172 Cf. A000040, A002253. %K A175172 nonn,hard,more %O A175172 1,1 %A A175172 _Vincenzo Librandi_, Mar 09 2010