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, ...
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
KEYWORD
nonn
AUTHOR
Altug Alkan, Nov 05 2016
STATUS
approved