This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A097024 #22 Jan 25 2024 08:01:26
%S A097024 1482,1878,1890,2142,2178
%N A097024 Numbers in the 5-cycle-attractor of the function f(x)=A063919(x).
%C A097024 A002827 provides 1-cycle terms = unitary perfect numbers.
%C A097024 A063991 gives 2-cycle elements = unitary amicable numbers.
%C A097024 A097030 collects true 14-cycle elements, i.e., terms in end-cycle of length 14 when A063919(x) function is iterated.
%C A097024 Concerning 3-cycle elements, only {30,42,54} were encountered.
%H A097024 J. O. M. Pedersen, <a href="/A097024/a097024.txt">Order 5 cycles</a>, 2007.
%t A097024 a063919[1] = 1; (* function a[] in A063919 by _Jean-François Alcover_ *)
%t A097024 a063919[n_] := Total[Select[Divisors[n], GCD[#, n/#]==1&]]-n/;n>1
%t A097024 a097024Q[k_] := Module[{a=NestList[a063919, k, 5]}, Count[a, k]==2&&Last[a]==k]
%t A097024 a097024[n_] := Select[Range[n], a097024Q]
%t A097024 a097024[2178] (* _Hartmut F. W. Hoft_, Jan 24 2024 *)
%o A097024 (PARI) f(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) - n;
%o A097024 isok5(n) = iferr(f(f(f(f(f(n))))) == n, E, 0);
%o A097024 isok1(n) = iferr(f(n) == n, E, 0);
%o A097024 isok(n) = !isok1(n) && isok5(n); \\ _Michel Marcus_, Sep 28 2018
%Y A097024 Cf. A063919, A002827, A063991, A097030.
%K A097024 nonn,more
%O A097024 1,1
%A A097024 _Labos Elemer_, Aug 30 2004