The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A097024

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A097024

Numbers in the 5-cycle-attractor of the function f(x)=A063919(x).
(history; published version)

#22 by N. J. A. Sloane at Thu Jan 25 08:01:26 EST 2024

STATUS

proposed

approved

#21 by Joerg Arndt at Thu Jan 25 04:31:15 EST 2024

STATUS

editing

proposed

#20 by Joerg Arndt at Thu Jan 25 04:30:54 EST 2024

NAME

Numbers in the 5-cycle-attractor if of the function f(x)=A063919(x) is iterated; f(x) is the sum of unitary proper divisors.

STATUS

proposed

editing

Discussion

Thu Jan 25

04:31

Joerg Arndt: I miss 'n' in name, do you have a suggestion?

#19 by Hartmut F. W. Hoft at Wed Jan 24 10:05:36 EST 2024

STATUS

editing

proposed

#18 by Hartmut F. W. Hoft at Wed Jan 24 10:05:30 EST 2024

MATHEMATICA

a063919[1] = 1; (* function a[] in A063919 by Jean-François Alcover *)

a063919[n_] := Total[Select[Divisors[n], GCD[#, n/#]==1&]]-n/; n>1

a097024Q[k_] := Module[{a=NestList[a063919, k, 5]}, Count[a, k]==2&&Last[a]==k]

a097024[n_] := Select[Range[n], a097024Q]

a097024[2178] (* Hartmut F. W. Hoft, Jan 24 2024 *)

STATUS

approved

editing

#17 by Alois P. Heinz at Tue Oct 02 03:18:22 EDT 2018

STATUS

proposed

approved

#16 by Michel Marcus at Tue Oct 02 03:17:16 EDT 2018

STATUS

editing

proposed

#15 by Michel Marcus at Tue Oct 02 03:16:43 EDT 2018

LINKS

J. O. M. Pedersen, <a href="/A097024/a097024.txt">Order 5 cycles</a>, 2007.

STATUS

approved

editing

#14 by Bruno Berselli at Fri Sep 28 05:52:55 EDT 2018

STATUS

reviewed

approved

#13 by Joerg Arndt at Fri Sep 28 05:32:19 EDT 2018

STATUS

proposed

reviewed