A090084 - OEIS

%I #32 Sep 19 2024 01:50:28

%S 10,70,190,1330,8170,9730,24130,28462,58030,98458,143830,144886,

%T 327370,856786,1580230,1620130,3536470,5274970,6082490,6376126,

%U 6792710,8066170,8610610,14076910,17728930,27275158,42447406,52970386,53497978,68925130

%N Even pseudoprimes to base 11.

%H Amiram Eldar, <a href="/A090084/b090084.txt">Table of n, a(n) for n = 1..165</a> (terms below 10^11; terms 1..84 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[ 11, 2n-1, 2n ]; If[ f==1, Print[ 2n ] ],{n,2,800000} ] (* _Alexander Adamchuk_, May 26 2007 *)

%t lst = {}; Do[ If[ PowerMod[11, 2n - 1, 2n] == 1, AppendTo[lst, 2n]], {n, 2, 2*10^9}]; lst (* _Robert G. Wilson v_, Jun 01 2007 *)

%t Select[Range[4,68926000,2],PowerMod[11,#-1,#]==1&] (* _Harvey P. Dale_, Oct 16 2021 *)

%o (PARI) is(k) = k > 2 && !(k % 2) &&  Mod(11, k)^(k-1) == 1; \\ _Amiram Eldar_, Sep 18 2024

%Y Cf. A020139.

%Y Cf. A006935, A130433, A090082, A090083, A090085, A130434, A130435, A130436, A130438, A130439, A130440, A130441, A130442, A130443.

%K nonn

%O 1,1

%A _Labos Elemer_, Nov 25 2003

%E More terms from _Alexander Adamchuk_, May 26 2007

%E Further terms from _Robert G. Wilson v_, Jun 01 2007