A140538 - OEIS

%I #14 Sep 08 2022 08:45:34

%S 3,11,163,19,139,2593,1601,2731,1193,113,227,619,577,8537,73,43691,

%T 55681,209953,307,9697,388963,52057,1091,337,260417,304651,3011,4937,

%U 471521,1620001,691,5419,32491,46889,90947,25643,11057,15619,7499,7793

%N Greatest prime factor of 2*n^4 + 1.

%H Vincenzo Librandi, <a href="/A140538/b140538.txt">Table of n, a(n) for n = 1..2000</a>

%F a(n) = A006530(2n^4+1) = A076565(n^4). - _R. J. Mathar_, Aug 04 2008

%e a(2)= 11 because 2*2^4+1 = 33 = 3*11, greatest prime factor is 11.

%t Table[Max[Transpose[FactorInteger[2 n^4 + 1]][[1]]], {n, 50}] (* _Vincenzo Librandi_, Feb 17 2015 *)

%o (PARI) a(n) = f = factor(2*n^4+1); f[#f~,1]; \\ _Michel Marcus_, Aug 28 2013

%o (Magma) [#f eq 0 select 1 else f[ #f][1] where f is Factorization(2*n^4 + 1): n in [1..50]]; // _Vincenzo Librandi_, Feb 17 2015

%K easy,nonn

%O 1,1

%A _Donald S. McDonald_, Jul 06 2008

%E Extended from a(16) on by _R. J. Mathar_, Aug 04 2008