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A068955 Greatest prime factor of n^n - (n-1)^(n-1). 5
3, 23, 229, 151, 431, 776887, 14731, 109, 80317, 275311670611, 19395030961, 10423708597, 968299894201, 19428121, 165218809021364149, 808793517812627212561, 3979203955386313, 588489604729898953429, 2126173979464312447783, 5043293621028391, 90772326303985278570534379 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Daniel Suteu and Amiram Eldar, Table of n, a(n) for n = 2..86 (terms 2..62 from Daniel Suteu)

FORMULA

a(n) = A006530(A007781(n-1)).

EXAMPLE

A007781(14) = 10809131718965763 = 3 * 61^2 * 968299894201, therefore a(14) = 968299894201.

MAPLE

a:= n-> max(map(i-> i[1], ifactors(n^n-(n-1)^(n-1))[2])):

seq(a(n), n=2..23);  # Alois P. Heinz, Mar 10 2019

MATHEMATICA

a[n_] := FactorInteger[n^n - (n-1)^(n-1)][[-1, 1]]; Array[a, 20, 2] (* Amiram Eldar, Feb 06 2020 *)

PROG

(PARI) a(n) = vecmax(factor(n^n-(n-1)^(n-1))[, 1]); \\ Daniel Suteu, Mar 10 2019

CROSSREFS

Cf. A006530, A007781, A068954, A068956.

Sequence in context: A306154 A201205 A068954 * A151393 A007781 A068146

Adjacent sequences:  A068952 A068953 A068954 * A068956 A068957 A068958

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Mar 11 2002

EXTENSIONS

a(18)-a(22) from Daniel Starodubtsev, Mar 10 2019

STATUS

approved

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Last modified May 17 22:15 EDT 2021. Contains 343992 sequences. (Running on oeis4.)