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 A037159 Consider trajectory of n under iteration of map which send x to 3x - sigma(x) if this is >= 0 otherwise stops. Sequence gives values of n which eventually reach 0. 4
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A perfect number is a fixed point of this map. LINKS 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 EXTENSIONS Better description from Jud McCranie, Dec 24 2000 STATUS approved

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Last modified October 15 15:14 EDT 2019. Contains 328030 sequences. (Running on oeis4.)