A037159 Consider the trajectory of n under the iteration of a map which sends x to 3x - sigma(x) if this is >= 0; otherwise the iteration stops. The sequence gives values of n which eventually reach 0.

82, 120, 280, 672, 1464, 3048, 4964, 5568, 5688, 7666, 8969, 9176, 9288, 9514, 9616, 9706, 10132, 10186, 10232, 10478, 11496, 11884, 11914, 12232, 12320, 12820, 13248, 13842, 13854, 13866, 14848, 15076, 15098, 15196, 15364, 15586, 15892

Offset

1,1

Comments

A perfect number is a fixed point of this map.

Links

Table of n, a(n) for n=1..37.

Example

82 -> 120 -> 0.

Mathematica

max = 16000; f[0] = 0; f[n_ /; 0 < n < 9max] := 3n - DivisorSigma[1, n]; f[_] = -1; Select[ Range[max], FixedPoint[f, #] == 0 &] (* Jean-François Alcover, Feb 22 2012 *)

Crossrefs

To see why 1, 16 and 23 are not in the sequence, see A058541, A058542 and A058545.

Cf. A033885, A033945, A033946, A037160.

Sequence in context: A296809 A223085 A260761 * A223088 A039547 A029704

Adjacent sequences: A037156 A037157 A037158 * A037160 A037161 A037162

Keyword

nonn,nice

Author

Naohiro Nomoto

Extensions

Better description from Jud McCranie, Dec 24 2000

Definition clarified by Harvey P. Dale, Jul 30 2020

Status

approved