%I #15 Dec 22 2024 20:12:56
%S 2,3,6,9,18,65,66,287,354,1425,3743,5598
%N Numbers k such that x^k + x^2 + 1 is irreducible over GF(7).
%C No terms == 1 (mod 3), as e.g. 2^k + 2^2 + 1 == 0 mod 7 when k == 1 (mod 3). - _Robert Israel_, Dec 22 2024
%p R:= NULL:
%p for k from 1 to 10000 do
%p if Irreduc(x^k + x^2 + 1) mod 7 then R:= R, k fi
%p od:
%p R; # _Robert Israel_, Dec 22 2024
%Y Cf. A057460, A058857.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 16 2001
%E 2 inserted and more terms from _Robert Israel_, Dec 22 2024