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 A344424 #10 May 24 2021 01:02:50 %S A344424 3,54,58,64,70,253,438,4255,8770 %N A344424 Numbers k such that A344423(k) is prime. %C A344424 a(10) > 10000. - _Hugo Pfoertner_, May 19 2021 %e A344424 A344423(3) = 100111001 is prime, so 3 is a term of the sequence. %o A344424 (PARI) is(n) = ispseudoprime(10^(2*n+2) + 111*10^n + 1) %Y A344424 Cf. A070247, A100580, A344423. %K A344424 nonn,hard,more %O A344424 1,1 %A A344424 _Felix Fröhlich_, May 18 2021 %E A344424 a(9) from _Hugo Pfoertner_, May 19 2021