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 A278471 #30 May 19 2024 02:16:56 %S A278471 16,18,38,82,98,318,1106,1914,2438,2640,3156,10330,19278,31976,41140 %N A278471 Numbers k such that 10^k - 2001 is prime. %C A278471 For n>3, numbers such that n-4 occurrences of the digit 9 followed by the digits 7999 is prime. %H A278471 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>. %e A278471 Initial terms and primes associated: %e A278471 a(1) = 16, 9999999999997999; %e A278471 a(2) = 18, 999999999999997999; %e A278471 a(3) = 38, 99999999999999999999999999999999997999; etc. %t A278471 Select[Range[3, 10000], PrimeQ[10^# - 2001] &] %o A278471 (Magma) [n: n in [3..700] | IsPrime(10^n-2001)]; %o A278471 (PARI) isok(n) = isprime(10^n - 2001); \\ _Michel Marcus_, Dec 03 2016 %Y A278471 Cf. similar sequences listed in A278470. %K A278471 nonn,more %O A278471 1,1 %A A278471 _Vincenzo Librandi_, Nov 28 2016 %E A278471 a(12) from _Michael S. Branicky_, Jan 29 2023 %E A278471 a(13) from _Michael S. Branicky_, Apr 10 2023 %E A278471 a(14)-a(15) from Kamada data by _Tyler Busby_, Apr 20 2024