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 A158021 #6 Dec 12 2024 22:57:03
%S A158021 11,23,83,107,167,179,227,347,479,587,839,863,983,1283,1367,1439,1487,
%T A158021 1619,1823,1907,2027,2039,2447,2879,2963,2999,3119,3203,3623,3863,
%U A158021 4127,4139,4259,4283,4787,5099,5483,5879,6719,6779,6983,7247,7703,7727,7823
%N A158021 Primes such that p, 10*p-1 and (p-1)/2 are all prime.
%H A158021 Robert Israel, <a href="/A158021/b158021.txt">Table of n, a(n) for n = 1..10000</a>
%p A158021 filter:= proc(n) isprime(n) and isprime((n-1)/2) and isprime(10*n-1) end proc:
%p A158021 select(filter, [seq(i,i=3 .. 10000, 4)]); # _Robert Israel_, Dec 12 2024
%t A158021 Flatten[Table[If[PrimeQ[n] && PrimeQ[10*n - 1] && PrimeQ[( n - 1)/2], n, {}], {n, 1, 10000}]]
%Y A158021 Cf. A059455. Intersection of A000040 and A158019.
%K A158021 nonn
%O A158021 1,1
%A A158021 _Roger L. Bagula_ and _Gary W. Adamson_, Mar 11 2009