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 A217493 #10 Jun 19 2022 02:24:53 %S A217493 2,3,4,9,11,18,19,27,28,46,50,53,80,155,203,280,451,4963,6167,9687, %T A217493 10083,31450 %N A217493 Numbers k such that 9^k - 10 is prime. %C A217493 Contains exactly the halved even terms of A217347. %t A217493 Select[Range[5000], PrimeQ[9^# - 10] &] %o A217493 (PARI) is(n)=ispseudoprime(9^n-10) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A217493 Cf. A217137, A217347. %K A217493 nonn,more %O A217493 1,1 %A A217493 _Vincenzo Librandi_, Oct 05 2012 %E A217493 a(19)-a(22) added from the data at A217347 by _Amiram Eldar_, Jun 19 2022