A333357 Integers that cannot be expressed as the ratio of 2 Fibonacci numbers.

6, 9, 10, 12, 14, 15, 16, 19, 20, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 77, 78, 79, 80

Offset: 1

Author

M. Farrokhi D. G., Jul 24 2020

Keywords

• nonn
• easy

Comments

Any product of m > 1 Fibonacci numbers > 1 belongs to the sequence except for 4, 18, 48, and 72.

Links

• M. Farrokhi D. G., Table of n, a(n) for n = 1..10000
• M. Farrokhi D. G., Some remarks on the equation F_n=kF_m in Fibonacci numbers, J. Integer Seq. 10 (2007), no. 5, Article 07.5.7, 9 pp.

Crossrefs

Cf. A000045.

Complement of A031121.

Programs

GAP

l := Filtered(Set(List(Cartesian([1..21], [1..21]), x -> Fibonacci(x[1] * x[2])/Fibonacci(x[1]))), x -> x < 10000);;
Filtered([1..10000], x ->  not x in l);