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%I #15 Feb 18 2021 10:30:00
%S 3,15,21,23,25,29,33,35,39,43,45,51,55,59,63,65,75,82,83,85,87,93,99,
%T 105,107,109,111,115,119,123,125,127,131,132,133,135,137,139,142,143,
%U 145,147,151,153,158,161,166,171,173,175,179,181,183,185,187,189,191
%N Integers m such that F(m) and F(2m) have the same largest prime factor where F(k) denotes the k-th Fibonacci number.
%C Why are even values rare? (First one is 82.)
%H Michel Marcus, <a href="/A074214/b074214.txt">Table of n, a(n) for n = 1..225</a>
%e F(15) = 610 = 2*5*61 and F(30) = 832040 = 2^3*5*11*31*61 hence 15 is in the sequence.
%t Select[Range[3,200],FactorInteger[Fibonacci[#]][[-1,1]]==FactorInteger[ Fibonacci[2#]][[-1,1]]&] (* _Harvey P. Dale_, Sep 04 2018 *)
%o (PARI) f(n) = vecmax(factor(fibonacci(n))[,1]); \\ A060385
%o isok(m) = (m>2) && (f(m) == f(2*m)); \\ _Michel Marcus_, Feb 18 2021
%Y Cf. A000045, A060385.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Sep 17 2002
%E More terms from _Don Reble_, Sep 20 2002