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A097024
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Numbers in the 5-cycle-attractor if the function f(x)=A063919(x) is iterated; f(x) is the sum of unitary proper divisors.
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23
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OFFSET
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1,1
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COMMENTS
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A002827 provides 1-cycle terms = unitary perfect numbers.
A063991 gives 2-cycle elements = unitary amicable numbers.
A097030 collects true 14-cycle elements, i.e., terms in end-cycle of length 14 when A063919(x) function is iterated.
Concerning 3-cycle elements, only {30,42,54} were encountered.
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LINKS
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Table of n, a(n) for n=1..5.
J. O. M. Pedersen, Order 5 cycles, 2007.
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PROG
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(PARI) f(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) - n;
isok5(n) = iferr(f(f(f(f(f(n))))) == n, E, 0);
isok1(n) = iferr(f(n) == n, E, 0);
isok(n) = !isok1(n) && isok5(n); \\ Michel Marcus, Sep 28 2018
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CROSSREFS
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Cf. A063919, A002827, A063991, A097030.
Sequence in context: A255789 A159719 A052167 * A253331 A158770 A252366
Adjacent sequences: A097021 A097022 A097023 * A097025 A097026 A097027
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KEYWORD
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nonn,more
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AUTHOR
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Labos Elemer, Aug 30 2004
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STATUS
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approved
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