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 A237440 #25 Mar 13 2016 11:28:01 %S A237440 2,3,5,7,61,97,101,257,2531,4783,5683,6317,8963,9463,9497,11593,15683, %T A237440 18757,23687,26251,29611,31271,36011,45497,45979,46853,54869,73379, %U A237440 92557,93761,104173,107857,107981,121607,134047,192091,196853,236729,285599,310081 %N A237440 Quadruple Hex-primes: let f(n) = A102489(n); then sequence lists primes p such that f(p), f(f(p)). f(f(f(p))) and f(f(f(f(p)))) are also primes. %C A237440 The sequence is a subset of sequences A103144, A237438, and A237439. %H A237440 Harvey P. Dale, <a href="/A237440/b237440.txt">Table of n, a(n) for n = 1..1000</a> %e A237440 Dec61=prime -> Hex61=Dec97=prime -> Hex97=Dec151=prime -> Hex151=Dec337=prime -> Hex337=Dec823=prime. %t A237440 qhpQ[n_]:=AllTrue[Rest[NestList[FromDigits[IntegerDigits[#],16]&,n,4]], PrimeQ]; Select[Prime[Range[27000]],qhpQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Mar 13 2016 *) %o A237440 (PARI) isok(p)= isprime(p) && isprime(p=hd(p)) && isprime(p=hd(p)) && isprime(p=hd(p)) && isprime(p=hd(p)); \\ _Michel Marcus_, Feb 09 2014 %Y A237440 Cf. A102489. %Y A237440 Cf. A103144 (Hex-primes), A237438 (Double Hex-primes), A237439 (Triple Hex-primes), A237441 (Quintuple Hex-primes). %K A237440 nonn,base %O A237440 1,1 %A A237440 _Andreas Boe_, Feb 07 2014 %E A237440 More terms from _Michel Marcus_, Feb 09 2014