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 A130438 #19 Feb 16 2025 08:33:06
%S A130438 22,154,638,946,1738,2926,12166,15862,33022,125686,248218,285286,
%T A130438 358534,596926,697334,1007566,3426346,3675826,3755158,4147522,6518974,
%U A130438 19866946,26336926,34220746,35083426,46365814,54148654,54342046,72789466
%N A130438 Even pseudoprimes to base 23.
%H A130438 Amiram Eldar, <a href="/A130438/b130438.txt">Table of n, a(n) for n = 1..153</a> (terms below 10^11; terms 1..78 from Robert G. Wilson v)
%H A130438 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatPseudoprime.html">Fermat Pseudoprime</a>.
%H A130438 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>.
%t A130438 lst = {}; Do[ If[ PowerMod[17, 2n - 1, 2n] == 1, AppendTo[lst, 2n]], {n, 2, 2*10^9}]; lst (* _Robert G. Wilson v_, Jun 01 2007 *)
%o A130438 (PARI) is(k) = k > 2 && !(k % 2) && Mod(23, k)^(k-1) == 1; \\ _Amiram Eldar_, Sep 29 2024
%Y A130438 Cf. A020151, A006935, A130433, A090082, A090083, A090084, A090085, A130434, A130435, A130436, A130437, A130439, A130440, A130441, A130442, A130443.
%K A130438 nonn
%O A130438 1,1
%A A130438 _Alexander Adamchuk_, May 26 2007
%E A130438 More terms from _Robert G. Wilson v_, Jun 01 2007