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A228523 Numbers that are not the product of two Fibonacci numbers (not necessarily distinct). 1
7, 11, 12, 14, 17, 18, 19, 20, 22, 23, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 66, 67, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 90, 91, 92 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All primes except prime Fibonacci numbers are in this sequence.

LINKS

Table of n, a(n) for n=1..66.

EXAMPLE

Although 12 can be expressed as a product of Fibonacci numbers, it takes three of them, not two, hence 12 is in the list.

There is no way to express 14 as a product of Fibonacci numbers since its larger prime factor, 7, is not a Fibonacci number, hence 14 is in the list.

16 is not in the list because it can be expressed as 2 * 8.

MATHEMATICA

nn = 12; f = Fibonacci[Range[2, nn]]; f2 = Select[Union[Flatten[Outer[Times, f, f]]], # <= f[[-1]] &]; Complement[Range[f[[-1]]], f2] (* T. D. Noe, Sep 03 2013 *)

CROSSREFS

Cf. A049997 (complement).

Sequence in context: A243885 A171017 A195608 * A193301 A213250 A226689

Adjacent sequences:  A228520 A228521 A228522 * A228524 A228525 A228526

KEYWORD

nonn,easy

AUTHOR

Alonso del Arte, Sep 02 2013

STATUS

approved

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Last modified February 20 16:42 EST 2020. Contains 332080 sequences. (Running on oeis4.)