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 A171227 #14 Nov 01 2024 17:46:23 %S A171227 0,1,4,17,26,28,47,70,91,1129,4334,12347,20212 %N A171227 Numbers k such that 9 + 10^k + 9*100^k is prime. %C A171227 No more terms up to k = 4100. %e A171227 19, 919, 900010009 are prime so that 0, 1 and 4 are terms. %o A171227 (PARI) is(n)=ispseudoprime(9+10^n+9*100^n) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A171227 Cf. A083816. %K A171227 more,nonn %O A171227 1,3 %A A171227 _Jason Earls_, Dec 05 2009 %E A171227 a(11)-a(12) from _Michael S. Branicky_, Jun 22 2023 %E A171227 a(13) from _Michael S. Branicky_, Nov 01 2024