A072556 Numbers n such that n and the n-th Fibonacci number have the same number of distinct prime factors.

1, 3, 4, 5, 7, 10, 11, 12, 13, 14, 17, 22, 23, 26, 29, 34, 43, 47, 83, 94, 131, 137, 359, 431, 433, 449, 509, 569, 571

Offset: 1

Author

Benoit Cloitre, Aug 06 2002

Keywords

• more
• nonn

Examples

			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
		

Crossrefs

Cf. A001221, A022307.

Programs

Maple

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

Mathematica

Insert[Select[Range[1, 50], Length[FactorInteger[ # ]] ==Length[FactorInteger[Fibonacci[ # ]]] &], 2, 2] (* Stefan Steinerberger, Mar 20 2006 *)
Select[Range[600],PrimeNu[#]==PrimeNu[Fibonacci[#]]&] (* Harvey P. Dale, Oct 14 2023 *)

Extensions

More terms from Sascha Kurz, Jan 25 2003

Edited by R. J. Mathar, Aug 11 2008