A068955 Greatest prime factor of n^n - (n-1)^(n-1).

3, 23, 229, 151, 431, 776887, 14731, 109, 80317, 275311670611, 19395030961, 10423708597, 968299894201, 19428121, 165218809021364149, 808793517812627212561, 3979203955386313, 588489604729898953429, 2126173979464312447783, 5043293621028391, 90772326303985278570534379

Offset: 2

Author

Reinhard Zumkeller, Mar 11 2002

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A006530, A007781, A068954, A068956.

Programs

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 *)

PARI

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

Formula

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

Extensions

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