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 A175235 #23 Sep 07 2024 15:42:10
%S A175235 3,5,7,11,19,61,163,911,997,16657,36551
%N A175235 Prime p such that 2^p + 21 is also prime.
%C A175235 a(12) > 100000. - _Dana Jacobsen_, Oct 03 2015
%C A175235 a(12) > 1173095 using A057201. - _Michael S. Branicky_, Sep 07 2024
%F A175235 A000040 INTERSECT A057201. - _R. J. Mathar_, May 02 2010
%e A175235 For p=3, 2^3+21=29; p=5, 2^5+21=53; p=7, 2^7+21=149.
%t A175235 Select[Prime[Range[10000]], PrimeQ[(2^# + 21)] &] (* _Vincenzo Librandi_, Oct 04 2015 *)
%o A175235 (Magma) [p: p in PrimesUpTo(4000) | IsPrime(2^p+21) ];
%o A175235 (Perl) use ntheory ":all"; use Math::GMP qw/:constant/; forprimes { my $n = 2**$_+21; say if is_prime($n) } 20000; # _Dana Jacobsen_, Oct 03 2015
%o A175235 (PARI) is(n)=prime(n)&&prime(2^n+21) \\ _Anders Hellström_, Oct 03 2015
%K A175235 nonn,more
%O A175235 1,1
%A A175235 _Vincenzo Librandi_, Mar 09 2010
%E A175235 a(10)-a(11) from _Dana Jacobsen_, Oct 03 2015