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%I #10 Jul 24 2021 05:40:23
%S 10,15,20,26,30,34,38,40,46,50,56,58,60,62,65,74,78,82,86,94,100,106,
%T 118,120,122,124,129,130,132,134,140,141,142,143,146,150,155,158,159,
%U 166,177,178,182,183,190,194,195,200,201,202,206,213,214,217,218,219
%N Composite numbers k such that 5^k (mod k) is a power of 5 greater than 1.
%H Amiram Eldar, <a href="/A129495/b129495.txt">Table of n, a(n) for n = 1..10000</a>
%e 26 is a member of the sequence since 5^26 (mod 26) == 25.
%t Select[Range@ 225, (p = PowerMod[5, #, #]) > 1 && IntegerQ@ Log[5, p] && CompositeQ[#] &] (* corrected by _Amiram Eldar_, Jul 24 2021 *)
%Y Cf. A036236, A129492, A129493, A129494, A129496, A129497.
%K easy,nonn
%O 1,1
%A _Robert G. Wilson v_, Apr 17 2007