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 A259490 #23 Aug 12 2021 16:40:13
%S A259490 2,4,9,33,595,1127,2003,3611,4356,6926
%N A259490 Numbers k such that the denominator of the n-th convergent of the continued fraction expansion of Pi is prime.
%C A259490 These are the k such that A002486(k+1) is prime. - _Michel Marcus_, Jul 15 2015
%C A259490 a(11) > 25000.
%t A259490 $MaxExtraPrecision = 25000; lst = {}; cf = ContinuedFraction[Pi, 10000]; Do[ If[ PrimeQ[ Denominator[ FromContinuedFraction[ Take[ cf, n]] ]], AppendTo[lst, n]], {n, Length[cf]}]; lst
%t A259490 Position[Convergents[Pi,7000],_?(PrimeQ[Denominator[#]]&)]//Flatten (* _Harvey P. Dale_, Aug 12 2021 *)
%Y A259490 Cf. A094007, A002486.
%K A259490 nonn,more
%O A259490 1,1
%A A259490 _Jonathan Sondow_ and _Robert G. Wilson v_, Jun 28 2015