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
Examples
82 -> 120 -> 0.
Crossrefs
Programs
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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 *)
Extensions
Better description from Jud McCranie, Dec 24 2000
Definition clarified by Harvey P. Dale, Jul 30 2020
Comments