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A081257 Greatest prime factor of n^3-1. 6

%I

%S 7,13,7,31,43,19,73,13,37,19,157,61,211,241,13,307,17,127,421,463,13,

%T 79,601,31,37,757,271,67,29,331,151,1123,397,97,43,67,1483,223,547,

%U 1723,139,631,283,109,103,61,181,43,2551,379,919,409,2971,79,103,3307,163

%N Greatest prime factor of n^3-1.

%H R. J. Mathar, <a href="/A081257/b081257.txt">Table of n, a(n) for n = 2..1000</a>

%e a(7)=19 because 7^3-1=342=2*3*3*19

%p A081257 := proc(n)

%p A006530( n^3-1) ;

%p end proc: # _R. J. Mathar_, Jul 18 2015

%t FactorInteger[#][[-1,1]]&/@(Range[2,60]^3-1) (* _Harvey P. Dale_, Oct 09 2017 *)

%o (PARI) a(n)=my(f=factor(n^3-1)); f[#f~,1] \\ _Charles R Greathouse IV_, Mar 08 2017

%Y Cf. A081256, A081258.

%Y Cf. A096175 n^3-1 is an odd semiprime, A096176 (n^3-1)/(n-1) is prime.

%K easy,nonn

%O 2,1

%A Jan Fricke (fricke(AT)uni-greifswald.de), Mar 14 2003

%E More terms from _Hugo Pfoertner_, Jun 21 2004

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Last modified November 15 14:06 EST 2019. Contains 329149 sequences. (Running on oeis4.)