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A129495 Composite numbers k such that 5^k (mod k) is a power of 5 greater than 1. 6

%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

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Last modified August 25 00:57 EDT 2024. Contains 375418 sequences. (Running on oeis4.)