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 A248350 #18 Jun 06 2020 10:45:01 %S A248350 9,10,13,19,26,68,73,115,190,195,232,549,742,1502,2239,2618,5143,8081, %T A248350 9442,31402,77919,93790,99434,120841 %N A248350 Numbers n such that 10^n - 123456789 is prime. %C A248350 a(26) > 200000. - _Robert Price_, Jun 06 2020 %o A248350 (PARI) for(n=1,10^4,if(ispseudoprime(10^n - 123456789),print1(n,", "))) %Y A248350 Cf. A248349, A248351, A248352, A050289. %K A248350 nonn,hard,more %O A248350 1,1 %A A248350 _Derek Orr_, Oct 05 2014 %E A248350 a(21)-a(25) from _Robert Price_, Feb 26 2020