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 A023301 #22 Sep 08 2022 08:44:47 %S A023301 13,139,293,331,547,967,1049,1399,1567,1889,1997,2087,2137,2309,2423, %T A023301 2437,2753,2939,3719,3761,3919,4451,4517,4621,6089,7001,7741,8423, %U A023301 8849,9437,10487,11657,12007,12347,12823,13469,15289,15373,15661,17737,17989 %N A023301 Primes that remain prime through 3 iterations of function f(x) = 10x + 9. %C A023301 Primes p such that 10*p+9, 100*p+99 and 1000*p+999 are also primes. - _Vincenzo Librandi_, Aug 04 2010 %H A023301 John Cerkan, <a href="/A023301/b023301.txt">Table of n, a(n) for n = 1..10000</a> %t A023301 nrp3Q[n_]:=AllTrue[Rest[NestList[10#+9&,n,3]],PrimeQ]; Select[Prime[ Range[ 2100]],nrp3Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Aug 12 2019 *) %o A023301 (Magma) [n: n in [1..450000] | IsPrime(n) and IsPrime(10*n+9) and IsPrime(100*n+99) and IsPrime(1000*n+999)] // _Vincenzo Librandi_, Aug 04 2010 %Y A023301 Subsequence of A023240, A023270, and A102700. %K A023301 nonn %O A023301 1,1 %A A023301 _David W. Wilson_