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 A023320 #19 Sep 08 2022 08:44:47 %S A023320 13121,117281,188831,317971,429281,624721,627791,722431,774791,883721, %T A023320 924731,946291,1002721,1083851,1212011,1221601,1249111,1342361, %U A023320 1469761,1665761,1896901,2003081,2156251,2336011,2382761,2391451,2612021,2634551 %N A023320 Primes that remain prime through 4 iterations of function f(x) = 8x + 3. %C A023320 Primes p such that 8*p+3, 64*p+27, 512*p+219 and 4096*p+1755 are also primes. - _Vincenzo Librandi_, Aug 04 2010 %H A023320 Harvey P. Dale, <a href="/A023320/b023320.txt">Table of n, a(n) for n = 1..1000</a> %t A023320 Select[Prime[Range[200000]],AllTrue[Rest[NestList[8#+3&,#,4]],PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Oct 04 2015 *) %o A023320 (Magma) [n: n in [1..5000000] | IsPrime(n) and IsPrime(8*n+3) and IsPrime(64*n+27) and IsPrime(512*n+219) and IsPrime(4096*n+1755)] // _Vincenzo Librandi_, Aug 04 2010 %K A023320 nonn %O A023320 1,1 %A A023320 _David W. Wilson_