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A055385 Smallest prime factor of n^n + 1.

%I A055385 #38 May 18 2025 02:14:03
%S A055385 2,5,2,257,2,13,2,97,2,101,2,89,2,29,2,274177,2,5,2,148721,2,5,2,17,2,
%T A055385 53,2,449,2,17,2,641,2,13,2,17,2,5,2,17,2,5,2,41,2,29,2,769,2,41,2,89,
%U A055385 2,13,2,17,2,5,2,17,2,5,2,59649589127497217,2,37,2,41,2,13,2,97,2,149
%N A055385 Smallest prime factor of n^n + 1.
%C A055385 If we use the commonly accepted convention that 0^0 = 1, then a(0) = 2. - _Chai Wah Wu_, Jul 22 2019
%D A055385 C. Stanley Ogilvy and John T. Anderson, Excursions in Number Theory. Dover. New York: 1988. Page 82.
%H A055385 Seiichi Manyama, <a href="/A055385/b055385.txt">Table of n, a(n) for n = 1..500</a>
%e A055385 4^4 + 1 = 257 prime, so a(4) = 257;
%e A055385 6^6 + 1 = 13 * 37 * 97, so a(6) = 13.
%t A055385 Table[FactorInteger[n^n + 1][[1, 1]], {n, 74}] (* _Vincenzo Librandi_, Jul 23 2013 *)
%o A055385 (PARI) a(n) = {if (n % 2, return (2)); return (factor(n^n + 1)[1, 1]);} \\ _Michel Marcus_, Jul 23 2013
%Y A055385 Cf. A014566, A055386.
%K A055385 nonn
%O A055385 1,1
%A A055385 _Walter Nissen_, Jun 24 2000