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 A023273 #33 Sep 08 2022 08:44:47 %S A023273 2,5,47,67,97,137,197,277,307,607,617,1307,1427,2857,5717,6047,6217, %T A023273 6257,6997,9377,9787,9967,11197,12097,13297,13997,14347,16057,18757, %U A023273 18947,20887,21517,21587,21757,24197,26227,28097,28447,32117,33767,34367,35117 %N A023273 Primes that remain prime through 3 iterations of function f(x) = 2x + 3. %C A023273 Primes p such that 2*p+3, 4*p+9 and 8*p+21 are also primes. - _Vincenzo Librandi_, Aug 04 2010 %H A023273 Vincenzo Librandi, <a href="/A023273/b023273.txt">Table of n, a(n) for n = 1..1000</a> %t A023273 Select[Prime[Range[5000]],AllTrue[Rest[NestList[2#+3&,#,3]],PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Mar 01 2016 *) %o A023273 (Magma) [p: p in PrimesUpTo(50000) | IsPrime(2*p+3) and IsPrime(4*p+9) and IsPrime(8*p+21)]; // _Vincenzo Librandi_, Aug 04 2010 %o A023273 (Python) %o A023273 from sympy import prime, isprime %o A023273 A023273_list = [p for p in (prime(n) for n in range(1,10**2)) if isprime(2*p+3) and isprime(4*p+9) and isprime(8*p+21)] # _Chai Wah Wu_, Sep 09 2014 %o A023273 (PARI) isok(n)=isprime(n) && isprime(2*n+3) && isprime(4*n+9) && isprime(8*n+21) \\ _Edward Jiang_, Sep 09 2014 %K A023273 nonn %O A023273 1,1 %A A023273 _David W. Wilson_