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A098185
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If f[x]=(sum of unitary-proper divisors of x)=A063919[x] is iterated, the iteration may lead to a fixed point which is either 1# equals 0; or 2# it is from A002827, a unitary-perfect-number >1: 6,60,90,87360... Here initial values are collected for which the iteration ends in a unitary perfect number>1.
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7
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6, 60, 66, 78, 90, 244, 292, 476, 482, 578, 648, 680, 688, 770, 784, 832, 864, 956, 958, 976, 1168, 1354, 1360, 1392, 1488, 1600, 1658, 1670, 1906, 2232, 2264, 2294, 2376, 2480, 2552, 2572, 2576, 2626, 2712, 2732, 2806, 2842, 2870, 2904, 2912, 2992, 3024
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| Initial values attracted by 87360[=4th unitary perfect number] are
collected separately in A098186.
It seems that iv=6 is the only start ending in fixed-point=6.
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MAPLE
| di[x_] :=Divisors[x]; ta={{0}}; ud[x_] :=Part[di[x], Flatten[Position[GCD[di[x], Reverse[di[x]]], 1]]]; asu[x_] :=Apply[Plus, ud[x]]-x; nsf[x_, ho_] :=NestList[asu, x, ho] Do[g=n; s=Last[NestList[asu, n, 100]]; If[Equal[s, 6]||Equal[s, 60]||Equal[s, 90], Print[{n, s}]; ta=Append[ta, n]], {n, 1, 256}]; ta = Delete[ta, 1]
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CROSSREFS
| Cf. A063919, A002827, A063991, A097024, A097030-A097037.
Sequence in context: A053987 A024270 A024271 * A173904 A204093 A136927
Adjacent sequences: A098182 A098183 A098184 * A098186 A098187 A098188
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Aug 31 2004
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