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A068955 Greatest prime factor of n^n - (n-1)^(n-1). 5

%I

%S 3,23,229,151,431,776887,14731,109,80317,275311670611,19395030961,

%T 10423708597,968299894201,19428121,165218809021364149,

%U 808793517812627212561,3979203955386313,588489604729898953429,2126173979464312447783,5043293621028391,90772326303985278570534379

%N Greatest prime factor of n^n - (n-1)^(n-1).

%H Daniel Suteu and Amiram Eldar, <a href="/A068955/b068955.txt">Table of n, a(n) for n = 2..86</a> (terms 2..62 from Daniel Suteu)

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

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

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

%p seq(a(n), n=2..23); # _Alois P. Heinz_, Mar 10 2019

%t a[n_] := FactorInteger[n^n - (n-1)^(n-1)][[-1, 1]]; Array[a, 20, 2] (* _Amiram Eldar_, Feb 06 2020 *)

%o (PARI) a(n) = vecmax(factor(n^n-(n-1)^(n-1))[,1]); \\ _Daniel Suteu_, Mar 10 2019

%Y Cf. A006530, A007781, A068954, A068956.

%K nonn

%O 2,1

%A _Reinhard Zumkeller_, Mar 11 2002

%E a(18)-a(22) from _Daniel Starodubtsev_, Mar 10 2019

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Last modified June 13 06:07 EDT 2021. Contains 344981 sequences. (Running on oeis4.)