%I #22 May 06 2022 07:37:56
%S 135,1423249,31491395,55519333,1065373685,3559609381
%N Odd numbers k such that 2^k mod k = 2^(k+2) mod (k-2) is also an odd number.
%H Joe K. Crump, <a href="http://web.archive.org/web/20070614175509/http://www.immortaltheory.com/NumberTheory/2nmodn.htm">2^n mod n</a>
%e 135 is a term because 2^135 mod 135 = 53 and 2^137 mod 133 = 53.
%o (PARI) isok(n) = {va = Mod(2,n)^n; (lift(va) % 2) && (lift(va) == lift(Mod(2, n-2)^(n+2)));} \\ _Michel Marcus_, Sep 02 2013
%Y Cf. A015911.
%K nonn,more
%O 1,1
%A Joe K. Crump (joecr(AT)carolina.rr.com), Aug 25 2000
%E a(6) and title clarified by _Sean A. Irvine_, May 04 2022