A139588 Nonprime numbers with Fibonacci number of divisors.

1, 4, 9, 16, 24, 25, 30, 40, 42, 49, 54, 56, 66, 70, 78, 81, 88, 102, 104, 105, 110, 114, 121, 128, 130, 135, 136, 138, 152, 154, 165, 169, 170, 174, 182, 184, 186, 189, 190, 195, 222, 230, 231, 232, 238, 246, 248, 250, 255, 258, 266, 273, 282, 285, 286, 289

Offset: 1

Author

Omar E. Pol, May 09 2008

Keywords

• easy
• nonn

Comments

A000005(a(n)) is a Fibonacci number.

The union of {1}, A001248, A030514, A030626, A030631, A137484, etc. [From R. J. Mathar, Oct 26 2009]

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000005, A000045, A018252, A123193, A139589, A139590.

Programs

Mathematica

Module[{fibs=Fibonacci[Range[20]]},Select[Range[300],!PrimeQ[#]&&MemberQ[ fibs,DivisorSigma[0,#]]&]] (* Harvey P. Dale, Jan 20 2023 *)

Formula

A123193 \ A000040. [From R. J. Mathar, Oct 23 2009]

Extensions

More terms from R. J. Mathar, Oct 23 2009