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%I #11 Oct 29 2024 03:40:53
%S 1,7,23,7,53,383,179,89,271,3413,2503,2137,59,367,1433,41,15803,59729,
%T 26423,11161,1559,12611,9187523,127867,119837257,11527,2360833,43969,
%U 2339,32212254719,257503,616318177,260587,127873,682902239,44939,69660839431,1185617
%N a(n) is the largest prime factor of n*2^n-1.
%H Amiram Eldar, <a href="/A367003/b367003.txt">Table of n, a(n) for n = 1..865</a>
%F a(n) = A006530(A003261(n)).
%t a[n_] := FactorInteger[n*2^n - 1][[-1, 1]]; Array[a, 40] (* _Amiram Eldar_, Oct 29 2024 *)
%Y Cf. A003261, A006530, A005420, A367002, A367004, A366899.
%K nonn
%O 1,2
%A _Sean A. Irvine_, Oct 31 2023