A173207 Cubefree Fibonacci numbers which are not squarefree.

75025, 12586269025, 225851433717, 2111485077978050, 4660046610375530309, 354224848179261915075, 43566776258854844738105, 114059301025943970552219, 42230279526998466217810220532898, 1672445759041379840132227567949787325

Offset

1,1

Comments

Subsequence of A061899. [R. J. Mathar, Feb 16 2010]

Apparently contains Fibonacci(25*m), m>0. - Ralf Stephan, Jan 26 2014

Links

Chai Wah Wu, Table of n, a(n) for n = 1..21

Formula

A000045 INTERSECT A067259.

Mathematica

f[n_]:=Union[Last/@FactorInteger[n]][[ -1]]; lst={}; Do[fibo=Fibonacci[n]; If[f[fibo]==2, AppendTo[lst, fibo]], {n, 3, 2*5!}]; lst
Select[Fibonacci[Range[200]], !SquareFreeQ[#]&&Max[FactorInteger[#][[;; , 2]]]<3&] (* Harvey P. Dale, Nov 24 2024 *)

Prog

(Python)
from sympy import factorint
A173207_list = []
a, b = 1, 2
for _ in range(10**2):
    if max(factorint(b).values()) == 2:
        A173207_list.append(b)
    a, b = b, a + b # Chai Wah Wu, Jun 08 2015

Crossrefs

Sequence in context: A210051 A179252 A045731 * A182809 A182393 A347848

Adjacent sequences: A173204 A173205 A173206 * A173208 A173209 A173210

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Feb 12 2010

Extensions

Converted cross-references to a formula - R. J. Mathar, Feb 16 2010

Status

approved