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 A124485 #25 Jul 20 2018 03:53:37
%S A124485 2,3,6,12,15,21,27,42,45,57,66,87,90,96,117,120,126,141,147,180,210,
%T A124485 216,222,246,255,297,321,327,330,342,360,372,381,405,456,477,507,510,
%U A124485 516,525,552,612,615,645,705,720,726,741,750,756,780,792,801,867,906,945
%N A124485 Numbers n such that 2n-1 and 4n-1 are primes.
%H A124485 Muniru A Asiru, <a href="/A124485/b124485.txt">Table of n, a(n) for n = 1..5000</a>
%F A124485 a(n) = (A005384(n+1) + 1)/2. - _Hilko Koning_, Jul 19 2018
%p A124485 select(k->isprime(2*k-1) and isprime(4*k-1),[$1..1000]); # _Muniru A Asiru_, Jul 19 2018
%t A124485 Select[Range[1000], And @@ PrimeQ /@ ({2, 4}*# - 1) &] (* _Ray Chandler_, Nov 21 2006 *)
%o A124485 (GAP) Filtered([1..1000],p->IsPrime(2*p-1) and IsPrime(4*p-1)); # _Muniru A Asiru_, Jul 19 2018
%Y A124485 Cf. A005384 (Sophie Germain primes).
%Y A124485 Cf. A124486, A124487, A124488, A124489, A124490, A124491, A124492.
%K A124485 nonn
%O A124485 1,1
%A A124485 _Artur Jasinski_, Nov 04 2006
%E A124485 Extended by _Ray Chandler_, Nov 21 2006