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 A130435 #21 Feb 16 2025 08:33:06
%S A130435 4,6,12,244,276,2806,5028,10308,40132,51118,115644,185646,216492,
%T A130435 237084,789636,936046,941818,1062876,1237276,1469716,2119002,2201002,
%U A130435 2410354,2446426,3198196,4319052,4979316,5329468,5496492,7171876,9513076
%N A130435 Even pseudoprimes to base 13.
%H A130435 Amiram Eldar, <a href="/A130435/b130435.txt">Table of n, a(n) for n = 1..300</a> (terms 1..101 from Robert G. Wilson v)
%H A130435 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatPseudoprime.html">Fermat Pseudoprime</a>.
%H A130435 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>.
%t A130435 Do[ f=PowerMod[ 13, 2n-1, 2n ]; If[ f==1, Print[ 2n ] ], {n,2,1000000} ] (* _Robert G. Wilson v_, May 31 2007 *)
%o A130435 (PARI) is(k) = k > 2 && !(k % 2) && Mod(13, k)^(k-1) == 1; \\ _Amiram Eldar_, Sep 18 2024
%Y A130435 Cf. A020141, A006935, A130433, A090082, A090083, A090084, A090085, A130434, A130436, A130437, A130438, A130439, A130440, A130441, A130442, A130443.
%K A130435 nonn
%O A130435 1,1
%A A130435 _Alexander Adamchuk_, May 26 2007
%E A130435 a(26)-a(31) from _Robert G. Wilson v_, May 31 2007