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Largest prime divisor of Lucas(5*n), where Lucas(k) = A000032(k).
5

%I #6 May 26 2022 09:50:36

%S 11,41,31,2161,151,2521,911,3041,541,570601,39161,20641,24571,

%T 12317523121,18451,23725145626561,12760031,10783342081,87382901,

%U 5738108801,767131,59996854928656801,686551,23735900452321,28143378001,42426476041450801,119611

%N Largest prime divisor of Lucas(5*n), where Lucas(k) = A000032(k).

%C Final digit of a(n) is 1. Mod[a(n),10] = 1. Final digit of many prime divisors of Lucas(5*n) is 1.

%H Daniel Suteu, <a href="/A121171/b121171.txt">Table of n, a(n) for n = 1..309</a>

%F a(n) = A006530(A000032(5*n)) = A079451(5*n). - _Daniel Suteu_, May 26 2022

%t Table[Max[Flatten[FactorInteger[Fibonacci[5n-1]+Fibonacci[5n+1]]]],{n,1,40}]

%o (PARI)

%o lucas(n) = fibonacci(n+1)+fibonacci(n-1); \\ A000032

%o a(n) = vecmax(factor(lucas(5*n))[,1]); \\ _Daniel Suteu_, May 26 2022

%Y Cf. A000032, A000045, A079451.

%K nonn

%O 1,1

%A _Alexander Adamchuk_, Aug 14 2006