A139587 Non-Fibonacci numbers with non-Fibonacci number of divisors.
6, 10, 12, 14, 15, 18, 20, 22, 26, 27, 28, 32, 33, 35, 36, 38, 39, 44, 45, 46, 48, 50, 51, 52, 57, 58, 60, 62, 63, 64, 65, 68, 69, 72, 74, 75, 76, 77, 80, 82, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 106, 108, 111
Offset: 1
Examples
6 belongs to the sequence because it is not a Fibonacci number and its number of divisors, 4, is also not a Fibonacci number.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Crossrefs
Programs
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Mathematica
With[{fibs=Fibonacci[Range[12]]},Select[Range[Max[fibs]],FreeQ[fibs,#] && FreeQ[fibs,DivisorSigma[0,#]]&]] (* Harvey P. Dale, Jun 20 2021 *)
Extensions
Example clarified by Harvey P. Dale, Jun 20 2021
Comments