This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A074214 #15 Feb 18 2021 10:30:00 %S A074214 3,15,21,23,25,29,33,35,39,43,45,51,55,59,63,65,75,82,83,85,87,93,99, %T A074214 105,107,109,111,115,119,123,125,127,131,132,133,135,137,139,142,143, %U A074214 145,147,151,153,158,161,166,171,173,175,179,181,183,185,187,189,191 %N A074214 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 A074214 Why are even values rare? (First one is 82.) %H A074214 Michel Marcus, <a href="/A074214/b074214.txt">Table of n, a(n) for n = 1..225</a> %e A074214 F(15) = 610 = 2*5*61 and F(30) = 832040 = 2^3*5*11*31*61 hence 15 is in the sequence. %t A074214 Select[Range[3,200],FactorInteger[Fibonacci[#]][[-1,1]]==FactorInteger[ Fibonacci[2#]][[-1,1]]&] (* _Harvey P. Dale_, Sep 04 2018 *) %o A074214 (PARI) f(n) = vecmax(factor(fibonacci(n))[,1]); \\ A060385 %o A074214 isok(m) = (m>2) && (f(m) == f(2*m)); \\ _Michel Marcus_, Feb 18 2021 %Y A074214 Cf. A000045, A060385. %K A074214 nonn %O A074214 1,1 %A A074214 _Benoit Cloitre_, Sep 17 2002 %E A074214 More terms from _Don Reble_, Sep 20 2002