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Numbers k that divide 19^k-1.
2

%I #18 May 05 2021 01:54:30

%S 1,2,3,4,6,8,9,10,12,16,18,20,24,27,30,32,36,40,42,48,50,54,60,64,72,

%T 80,81,84,90,96,100,108,110,120,126,128,136,144,150,156,160,162,168,

%U 180,192,200,210,216,220,240,243,250,252,256,270,272,288,294,300,312,320,324,330,336

%N Numbers k that divide 19^k-1.

%H Seiichi Manyama, <a href="/A333506/b333506.txt">Table of n, a(n) for n = 1..10000</a>

%t Join[{1}, Select[Range[2, 336], PowerMod[19, #, #] == 1 &]] (* _Amiram Eldar_, May 05 2021 *)

%o (PARI) for(k=1, 1e3, if(Mod(19, k)^k==1, print1(k", ")))

%Y Columns k=19 of A333432.

%Y Cf. A128358, A128360, A128399.

%K nonn

%O 1,2

%A _Seiichi Manyama_, Mar 25 2020