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 A130443 #20 Feb 16 2025 08:33:06
%S A130443 6,14,42,526974,9157582,21001206,49419154,156418318,157058362,
%T A130443 223741702,467016562,531330346,601692022,681377698,888739174,
%U A130443 931053466,1037629198,1390950926,1392718618,2175608494,2377982166,3045063946,5136468646
%N A130443 Even pseudoprimes to base 43.
%H A130443 Amiram Eldar, <a href="/A130443/b130443.txt">Table of n, a(n) for n = 1..74</a> (terms below 10^11; terms 1..46 from Robert G. Wilson v)
%H A130443 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatPseudoprime.html">Fermat Pseudoprime</a>.
%H A130443 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>.
%t A130443 lst = {}; Do[ If[ PowerMod[43, 2n - 1, 2n] == 1, AppendTo[lst, 2n]], {n, 2, 1800000000}]; lst (* _Robert G. Wilson v_, Jun 01 2007 *)
%o A130443 (PARI) is(k) = k > 2 && !(k % 2) && Mod(43, k)^(k-1) == 1; \\ _Amiram Eldar_, Sep 29 2024
%Y A130443 Cf. A020171, A006935, A130433, A090082, A090083, A090084, A090085, A130434, A130435, A130436, A130437, A130438, A130439, A130440, A130441, A130442.
%K A130443 nonn
%O A130443 1,1
%A A130443 _Alexander Adamchuk_, May 26 2007, Jun 20 2007
%E A130443 More terms from _Robert G. Wilson v_, Jun 01 2007