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A276811 a(n) = sigma(Fibonacci(k))/Fibonacci(n) where k is the least number such that Fibonacci(n) divides sigma(Fibonacci(k)), or -1 if no such k exists. 0
1, 1, 2, 1, 3, 4, 31, 20, 47, 5832, 322, 84, 4576568315415066934826490, 324, 843, 480, 3769607182320, 2209, 707932145558030519866865515025923563263974776037874477588352, 69670959389872974262939756520, 39603 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Least k such that Fibonacci(n) divides sigma(Fibonacci(k)) are 1, 1, 4, 3, 6, 8, 12, 14, 17, 27, 23, 20, 131, 26, 29, 28, 77, 34, 305, 158, 43, ...

LINKS

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

EXAMPLE

a(7) = 31 because least k such that Fibonacci(7) divides sigma(Fibonacci(k)) is 12 and sigma(Fibonacci(12))/Fibonacci(7) = 31.

MATHEMATICA

f[n_] := Block[{k = 1, fn = Fibonacci@ n}, While[ds = DivisorSigma[1, Fibonacci[k]]; Mod[ds, fn] > 0, k++]; ds/fn]; Array[f, 21] (* Robert G. Wilson v, Nov 06 2016 *)

CROSSREFS

Cf. A000045, A063477, A277261.

Sequence in context: A141487 A217103 A099866 * A317750 A188732 A085189

Adjacent sequences:  A276808 A276809 A276810 * A276812 A276813 A276814

KEYWORD

nonn

AUTHOR

Altug Alkan, Nov 05 2016

STATUS

approved

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Last modified August 21 10:36 EDT 2018. Contains 313937 sequences. (Running on oeis4.)