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A238684 a(1) = a(2) = 1; for n > 2, a(n) is the product of prime factors of the n-th Fibonacci number. 0
1, 1, 2, 3, 5, 2, 13, 21, 34, 55, 89, 6, 233, 377, 610, 987, 1597, 646, 4181, 6765, 10946, 17711, 28657, 966, 15005, 121393, 196418, 317811, 514229, 208010, 1346269, 2178309, 3524578, 5702887, 9227465, 207366, 24157817, 39088169, 63245986, 102334155, 165580141, 66978574, 433494437, 701408733, 1134903170 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

In other words, the squarefree part of the n-th Fibonacci number.

LINKS

Table of n, a(n) for n=1..45.

FORMULA

a(n) = A007947(A000045(n)) - Tom Edgar, Mar 03 2014

EXAMPLE

a(12) = 6 since F(12) = 144 = 2^4 * 3^2 and 2 * 3 = 6.

MATHEMATICA

Table[Times@@Part[Flatten[FactorInteger[Fibonacci[n]]], 1 ;; -2 ;; 2], {n, 3, 50}] (* Alonso del Arte, Mar 02 2014 *)

PROG

(PARI) a(n) = my(f = factor(fibonacci(n))); prod(i=1, #f~, f[i, 1]); \\ Michel Marcus, Mar 02 2014

CROSSREFS

Cf. A000045, A080648.

Sequence in context: A080648 A113195 A069110 * A202694 A123221 A197032

Adjacent sequences:  A238681 A238682 A238683 * A238685 A238686 A238687

KEYWORD

nonn

AUTHOR

Carmine Suriano, Mar 02 2014

STATUS

approved

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Last modified April 19 11:46 EDT 2021. Contains 343114 sequences. (Running on oeis4.)