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Even pseudoprimes to base 13.
15

%I #20 Sep 19 2024 01:50:10

%S 4,6,12,244,276,2806,5028,10308,40132,51118,115644,185646,216492,

%T 237084,789636,936046,941818,1062876,1237276,1469716,2119002,2201002,

%U 2410354,2446426,3198196,4319052,4979316,5329468,5496492,7171876,9513076

%N Even pseudoprimes to base 13.

%H 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 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/FermatPseudoprime.html">Fermat Pseudoprime</a>.

%H <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>.

%t Do[ f=PowerMod[ 13, 2n-1, 2n ]; If[ f==1, Print[ 2n ] ], {n,2,1000000} ] (* _Robert G. Wilson v_, May 31 2007 *)

%o (PARI) is(k) = k > 2 && !(k % 2) && Mod(13, k)^(k-1) == 1; \\ _Amiram Eldar_, Sep 18 2024

%Y Cf. A020141, A006935, A130433, A090082, A090083, A090084, A090085, A130434, A130436, A130437, A130438, A130439, A130440, A130441, A130442, A130443.

%K nonn

%O 1,1

%A _Alexander Adamchuk_, May 26 2007

%E a(26)-a(31) from _Robert G. Wilson v_, May 31 2007