A006486 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

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