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A127163 Integers whose aliquot sequences terminate by encountering the prime 3. Also known as the prime family 3.

%I A127163 #9 Jun 07 2023 11:02:58
%S A127163 3,4,9,12,15,16,26,30,33,42,45,46,52,54,66,72,78,86,87,90,102,105,114,
%T A127163 121,123,126,135,144,165,166,174,186,198,207,212,243,246,247,249,258,
%U A127163 259,270
%N A127163 Integers whose aliquot sequences terminate by encountering the prime 3. Also known as the prime family 3.
%C A127163 This sequence is complete only as far as the last term given, for the eventual fate of the aliquot sequence generated by 276 is not (yet) known
%D A127163 Benito, Manuel; Creyaufmueller, Wolfgang; Varona, Juan Luis; and Zimmermann, Paul; Aliquot Sequence 3630 Ends After Reaching 100 Digits; Experimental Mathematics, Vol. 11, No. 2, Natick, MA, 2002, pp. 201-206.
%H A127163 Manuel Benito and Juan L. Varona, <a href="https://doi.org/10.1090/S0025-5718-99-00991-6">Advances In Aliquot Sequences</a>, Mathematics of Computation, Vol. 68, No. 225, (1999), pp. 389-393.
%H A127163 Wolfgang Creyaufmueller, <a href="http://www.aliquot.de/aliquote.htm">Aliquot sequences</a>.
%F A127163 Define s(i)=sigma(i)-i=A000203(i)-i. Then if the aliquot sequence obtained by repeatedly applying the mapping i->s(i) terminates by encountering the prime 3 as a member of its trajectory, i is included in this sequence
%e A127163 a(5)=15 because the fifth integer whose aliquot sequence terminates by encountering the prime 3 as a member of its trajectory is 15. The complete aliquot sequence generated by iterating the proper divisors of 15 is 15->9->4->3->1->0
%t A127163 s[n_] := DivisorSigma[1, n] - n; g[n_] := If[n > 0, s[n], 0]; Trajectory[n_] := Most[NestWhileList[g, n, UnsameQ, All]]; Select[Range[275], MemberQ[Trajectory[ # ], 3] &]
%Y A127163 Cf. A080907, A127161, A127162, A127164, A098007, A121507, A098008, A007906, A063769, A115060, A115350.
%K A127163 hard,nonn
%O A127163 1,1
%A A127163 _Ant King_, Jan 07 2007