A291791 Numbers n whose trajectory under the iteration of k -> (sigma(k)+phi(k))/2 reaches a fraction.

4, 8, 9, 12, 14, 15, 16, 18, 20, 24, 25, 28, 32, 33, 34, 35, 36, 42, 48, 49, 50, 54, 55, 56, 62, 63, 64, 69, 70, 72, 76, 77, 78, 81, 84, 85, 86, 87, 88, 90, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105, 108, 110, 111

Offset

1,1

Comments

It would be nice to have an independent characterization of these numbers (not involving the map in the definition).

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..126

Crossrefs

Union of A028982 \ {1,2} and A290001. Also the complement of A289997.

Cf. A000010, A000203.

Sequence in context: A294574 A010453 A078136 * A037973 A044844 A145190

Adjacent sequences: A291788 A291789 A291790 * A291792 A291793 A291794

Keyword

nonn

Author

N. J. A. Sloane, Sep 03 2017

Extensions

B-file shortened by N. J. A. Sloane, Sep 17 2017

Status

approved