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 A217350 #29 Nov 29 2023 10:41:06 %S A217350 1,3,5,9,15,33,41,335,443,671,1197,1355,2247,2639,117293,191099 %N A217350 Numbers k such that 4^k + 9 is prime. %C A217350 The next terms are > 250000. - _Robert Price_, Oct 05 2015 %C A217350 Contains exactly the halved even terms of A057196. %e A217350 For k = 15, 4^15 + 9 = 1073741833 is prime. %t A217350 Select[Range[0, 5000], PrimeQ[4^# + 9] &] %o A217350 (Magma) [n: n in [0..700] | IsPrime(4^n+9)]; // _Vincenzo Librandi_, Oct 06 2015 %o A217350 (PARI) is(n)=ispseudoprime(4^n+9) \\ _Charles R Greathouse IV_, Jun 06 2017 %Y A217350 Cf. A057196, A089437 (similar sequence). %K A217350 nonn,more %O A217350 1,2 %A A217350 _Vincenzo Librandi_, Oct 01 2012 %E A217350 a(15)-a(16) derived from A057196 by _Robert Price_, Oct 05 2015