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

1,2

Links

Table of n, a(n) for n=1..29.

Example

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

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 *)

Crossrefs

Cf. A001221, A022307.

Sequence in context: A165713 A105148 A370862 * A047365 A353448 A048342

Adjacent sequences: A072553 A072554 A072555 * A072557 A072558 A072559

Keyword

more,nonn

Author

Benoit Cloitre, Aug 06 2002

Extensions

More terms from Sascha Kurz, Jan 25 2003

Edited by R. J. Mathar, Aug 11 2008

Status

approved