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 A209250 #23 Apr 03 2023 10:36:13 %S A209250 38,214,425,557,713,1322,1330,5061,19090,19876,31954,41012,53924, %T A209250 94455,124516,127326,413500,476124 %N A209250 Numbers n such that (2^64 - 189)*10^n + 1 is prime. %C A209250 The prime (2^64 - 189)*10^476124 + 1 has 476144 digits. %H A209250 Edward A. Trice, <a href="https://t5k.org/primes/page.php?id=110546">Page for a(18) at The Prime Pages</a> %H A209250 Edward A. Trice, <a href="https://t5k.org/primes/page.php?id=110196">Page for a(17) at The Prime Pages</a> %e A209250 38 is in the sequence since (2^64 - 189)*10^38 + 1 is prime. %e A209250 10 is not in the sequence since (2^64 - 189)*10^10 + 1 = 83639*2205519443526291733162759 is composite. %t A209250 Select[Range[725], PrimeQ[(2^64 - 189)*10^# + 1] &] (* _G. C. Greubel_, Jan 05 2018 *) %o A209250 (PARI) is(n)=ispseudoprime((2^64-189)*10^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %K A209250 nonn,more %O A209250 1,1 %A A209250 _Edward A. Trice_, Jan 13 2013