A023886 Average of proper divisors excluding 1 is an integer.

4, 8, 9, 15, 18, 21, 25, 27, 33, 35, 39, 45, 49, 51, 55, 57, 63, 65, 69, 75, 77, 81, 85, 87, 91, 93, 95, 98, 99, 111, 115, 117, 119, 121, 123, 125, 128, 129, 133, 141, 143, 145, 147, 153, 155, 159, 161, 162, 169, 171, 175, 177, 183, 185, 187, 201, 203

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• changed

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Programs

Mathematica

Select[Range[210],IntegerQ[Mean[Rest[Most[Divisors[#]]]]]&]  (* Harvey P. Dale, Feb 20 2011 *)

Extensions

Definition clarified by Harvey P. Dale, Feb 20 2011