A072556 - OEIS

%I #17 Oct 14 2023 12:50:34

%S 1,3,4,5,7,10,11,12,13,14,17,22,23,26,29,34,43,47,83,94,131,137,359,

%T 431,433,449,509,569,571

%N Numbers n such that n and the n-th Fibonacci number have the same number of distinct prime factors.

%e a(7)=10 because 10 and 10th Fibonacci number(i.e. 55) have the same number of prime factors i.e. 2. - _Shyam Sunder Gupta_, Feb 05 2006

%p with(combinat): with(numtheory): a:=proc(n) if nops(factorset(fibonacci(n)))=nops(factorset(n)) then n else fi end: seq(a(n),n=1..150); # _Emeric Deutsch_, Apr 02 2006

%t Insert[Select[Range[1, 50], Length[FactorInteger[ # ]] ==Length[FactorInteger[Fibonacci[ # ]]] &], 2, 2] (* _Stefan Steinerberger_, Mar 20 2006 *)

%t Select[Range[600],PrimeNu[#]==PrimeNu[Fibonacci[#]]&] (* _Harvey P. Dale_, Oct 14 2023 *)

%Y Cf. A001221, A022307.

%K more,nonn

%O 1,2

%A _Benoit Cloitre_, Aug 06 2002

%E More terms from _Sascha Kurz_, Jan 25 2003

%E Edited by _R. J. Mathar_, Aug 11 2008