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 A023309 #28 Jun 29 2025 14:02:40 %S A023309 3181,9551,22051,30941,32621,61981,76651,99961,134291,151901,163661, %T A023309 185951,226691,227671,240551,288191,342821,374501,394411,402881, %U A023309 423781,426301,446461,456151,459091,460951,554011,572321,577601,617191,653831 %N A023309 Primes that remain prime through 4 iterations of function f(x) = 3x + 8. %C A023309 Primes p such that 3*p+8, 9*p+32, 27*p+104 and 81*p+320 are also primes. - _Vincenzo Librandi_, Aug 04 2010 %H A023309 John Cerkan, <a href="/A023309/b023309.txt">Table of n, a(n) for n = 1..10000</a> %F A023309 a(n) == 1 or 31 (mod 70). - _John Cerkan_, Oct 04 2016 %t A023309 okQ[n_]:=And@@PrimeQ/@Rest[NestList[3#+8&,n,4]]; Select[Prime[Range[60000]],okQ] (* _Harvey P. Dale_, Aug 16 2010 *) %o A023309 (Magma) [n: n in [1..1000000] | IsPrime(n) and IsPrime(3*n+8) and IsPrime(9*n+32) and IsPrime(27*n+104) and IsPrime(81*n+320)]; // _Vincenzo Librandi_, Aug 04 2010 %Y A023309 Subsequence of A023210, A023248, and A023279. %K A023309 nonn %O A023309 1,1 %A A023309 _David W. Wilson_