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 A287351 #34 Jul 22 2021 23:29:37 %S A287351 1,3,9,15,27,37,165,207,897,5761,16753,17995,96567 %N A287351 Numbers k such that (10^k*361 - 163)/9 is prime (k > 0). %C A287351 a(14) > 10^5. - _Robert Price_, Oct 31 2017 %e A287351 If k = 1 then (10^1*361 - 163)/9 = 383 (prime), so 1 is a term. %e A287351 If k = 9 then (10^9*361 - 163)/9 = 40111111093 (prime), so 9 is a term. %t A287351 ParallelMap[ If[ PrimeQ[ (10^# 361-163)/9], #, Nothing] &, Range[6000]] %Y A287351 Cf. A247643. %K A287351 nonn,hard,more %O A287351 1,2 %A A287351 _Mikk Heidemaa_, May 23 2017 %E A287351 a(13) from _Robert Price_, Oct 31 2017