A006486 a(n) = largest prime factor of n^n - 1. (Formerly M2938)

3, 13, 17, 71, 43, 4733, 241, 757, 9091, 1806113, 20593, 1803647, 8108731, 39225301, 6700417, 2699538733, 465841, 109912203092239643840221, 222361, 227633407, 285451051007, 1920647391913, 1134793633, 50150933101, 3574533119, 12557612956332313, 1100860153

Offset

2,1

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n = 2..138

D. S. Kluk and N. J. A. Sloane, Correspondence, 1979.

Formula

a(n) = A006530(A048861(n)). - Michel Marcus, Aug 24 2019

Mathematica

Table[Max@Transpose[FactorInteger[n^n - 1]][[1]], {n, 2, 28}] (* Arkadiusz Wesolowski, Aug 06 2012 *)

Prog

(PARI) for(k=2, 28, my(x=factor(k^k-1), f=x[#x[, 1], 1]); print1(f, ", ")) \\ Hugo Pfoertner, Aug 23 2019
(Magma) [Max(PrimeDivisors(n^n-1)):n in [2..28]]; // Marius A. Burtea, Aug 24 2019

Crossrefs

Cf. A006530, A007571, A048861, A125135.

Sequence in context: A166567 A070520 A018579 * A368709 A273946 A070518

Adjacent sequences: A006483 A006484 A006485 * A006487 A006488 A006489

Keyword

nonn,hard

Author

Dennis S. Kluk (mathemagician(AT)ameritech.net)

Extensions

Corrected by T. D. Noe, Nov 14 2006

5 more terms from Arkadiusz Wesolowski, Aug 06 2012

Terms up to a(126) in b-file added by Sean A. Irvine, Apr 25 2017

Terms a(127)-a(138) in b-file added by Max Alekseyev, Aug 26 2021

Status

approved