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%I #14 Jul 20 2020 02:03:19
%S 6,60,66,78,90,244,292,476,482,578,648,680,688,770,784,832,864,956,
%T 958,976,1168,1354,1360,1392,1488,1600,1658,1670,1906,2232,2264,2294,
%U 2376,2480,2552,2572,2576,2626,2712,2732,2806,2842,2870,2904,2912,2992,3024
%N 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 equals 0 or 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.
%H Donovan Johnson, <a href="/A098185/b098185.txt">Table of n, a(n) for n = 1..1000</a>
%e Initial values attracted by 87360 (4th unitary perfect number) are collected separately in A098186.
%e It seems that 6 is the only initial value ending in fixed point = 6.
%t 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]
%Y Cf. A063919, A002827, A063991, A097024, A097030-A097037.
%K nonn
%O 1,1
%A _Labos Elemer_, Aug 31 2004
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