%I #17 Aug 15 2021 02:19:30
%S 1,2,4,6,8,12,16,18,24,32,36,42,48,52,54,64,72,84,96,104,108,126,128,
%T 144,156,162,168,186,192,208,216,252,256,272,288,294,312,324,336,342,
%U 372,378,384,416,432,468,486,504,512,544,558,576,588,624,648,672,676
%N Numbers k that divide 5^k - 1.
%H Harvey P. Dale, <a href="/A067946/b067946.txt">Table of n, a(n) for n = 1..1000</a>
%t Join[{1},Select[Range[700],PowerMod[5,#,#]==1&]] (* _Harvey P. Dale_, Feb 25 2015 *)
%o (PARI) is(n)=Mod(5,n)^n==1 \\ _Charles R Greathouse IV_, Nov 04 2016
%Y Cf. A024049.
%K easy,nonn
%O 1,2
%A _Benoit Cloitre_, Mar 05 2002