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 A187022 a(n) is the smallest prime factor of n^n+1 having the form k*n+1. 5

%I #20 May 17 2024 03:18:16

%S 5,7,257,521,13,113,97,73,101,23,193,13417,29,31,274177,

%T 45957792327018709121,37,108301,148721,337,9617835527609,47,33409,

%U 239201,53,163,449,233,61,373,641,661,6009977,71,22452257707354557235348829785471057921,593,202921,79,641

%N a(n) is the smallest prime factor of n^n+1 having the form k*n+1.

%C The values of k are in A187024.

%H Amiram Eldar, <a href="/A187022/b187022.txt">Table of n, a(n) for n = 2..148</a> (terms 2..100 from Vincenzo Librandi)

%e 12^12+1 = 89*193*233*2227777; the smallest prime divisor of the form k*n+1 is 193 = 16*12+1, hence a(12) = 193.

%t Table[p=First/@FactorInteger[n^n+1]; Select[p, Mod[#1, n] == 1 &, 1][[1]], {n, 2, 40}]

%o (Magma) A187022:=function(n); for d in PrimeDivisors(n^n+1) do if d mod n eq 1 then return d; end if; end for; return 0; end function; [ A187022(n): n in [2..40] ]; // _Klaus Brockhaus_, Mar 02 2011

%Y Cf. A187024.

%K nonn

%O 2,1

%A _Michel Lagneau_, Mar 02 2011

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Last modified September 17 17:26 EDT 2024. Contains 375990 sequences. (Running on oeis4.)