A159973 Non-refactorable numbers: number of divisors of n does not divide n.

3, 4, 5, 6, 7, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 85

Offset: 1

Author

Jaroslav Krizek, Apr 28 2009

Keywords

• nonn

Crossrefs

Complement of A033950.

Programs

Magma

[ n: n in [1..85] | n mod #Divisors(n) ne 0 ];

Mathematica

Select[Range[100],Mod[#,DivisorSigma[0,#]]!=0&] (* Harvey P. Dale, Aug 31 2023 *)

Extensions

Edited and extended by Klaus Brockhaus, Apr 29 2009