

A061899


Fibonacci numbers that are not squarefree.


7



8, 144, 2584, 46368, 75025, 832040, 14930352, 267914296, 4807526976, 12586269025, 86267571272, 225851433717, 1548008755920, 27777890035288, 498454011879264, 2111485077978050, 8944394323791464, 160500643816367088, 2880067194370816120, 4660046610375530309, 51680708854858323072
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OFFSET

1,1


COMMENTS

a(n) <= Fibonacci(6n) since 4  Fibonacci(6n). Using other residue classes it can be shown that a(n) << 1.134^n. How far can this method be taken?  Charles R Greathouse IV, Dec 13 2011


LINKS



FORMULA



EXAMPLE

144 and 2584 are Fibonacci numbers (A000045) and are not squarefree: 144 = 2^4*3^2, 2584 = 2^3*17*19.


MATHEMATICA

Select[Fibonacci[Range[100]], !SquareFreeQ[#]&] (* Harvey P. Dale, May 01 2018 *)


PROG

(PARI) { n=0; h=g=1; for (i=0, 375, f=g + h; h=g; g=f; if (!issquarefree(f), write("b061899.txt", n++, " ", f)) ) } \\ Harry J. Smith, Jul 28 2009


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



