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A367420 Numbers k with the property that if a Fibonacci number f is divisible by k then f is also divisible by 2*k.

%I A367420 #36 Jan 08 2024 22:38:55
%S A367420 4,6,9,12,14,17,18,19,20,22,23,24,27,28,30,31,36,38,42,44,45,46,51,52,
%T A367420 53,54,56,57,58,60,61,62,63,66,68,69,70,72,76,78,79,81,82,83,84,85,86,
%U A367420 90,92,93,94,95,98,99,100,102,107,108,109,110,112,114,115,116,117
%N A367420 Numbers k with the property that if a Fibonacci number f is divisible by k then f is also divisible by 2*k.
%C A367420 If k is a term then so is b*k for any odd b.
%H A367420 Robin Visser, <a href="/A367420/b367420.txt">Table of n, a(n) for n = 1..10000</a>
%e A367420 4 is in the sequence as any Fibonacci number divisible by 4 is divisible by 2*4.
%o A367420 (Python)
%o A367420 def is_A367420(k):
%o A367420     a, b = 1, 1
%o A367420     while((a,b)!=(0,1)):
%o A367420         if (a==k): return False
%o A367420         a, b = b, (a+b)%(2*k)
%o A367420     return True
%o A367420 print([k for k in range(1, 1000) if is_A367420(k)])  # _Robin Visser_, Jan 08 2024
%Y A367420 Cf. A000045, A001177.
%K A367420 nonn
%O A367420 1,1
%A A367420 _J. Lowell_, Nov 17 2023
%E A367420 More terms from _David A. Corneth_, Nov 17 2023