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A212908 Numbers n such that A212813(n) = 3.

%I A212908 #17 Aug 02 2018 07:55:47
%S A212908 13,15,16,18,19,21,22,23,25,30,32,34,36,47,53,56,63,69,74,75,76,80,90,
%T A212908 92,96,104,108,117,123,133,136,153,165,169,172,176,190,198,228,238,
%U A212908 245,259,273,285,286,294,304,325,328,340,342,350,357,369,370,376,385,390,403,408,416,420,423,425,429,444,448,459,462,465,468,484,496,500
%N A212908 Numbers n such that A212813(n) = 3.
%D A212908 Bellamy, O. S.; Cadogan, C. C. Subsets of positive integers: their cardinality and maximality properties. Proceedings of the Tenth Southeastern Conference on Combinatorics, Graph Theory and Computing (Florida Atlantic Univ., Boca Raton, Fla., 1979), pp. 167--178, Congress. Numer., XXIII-XXIV, Utilitas Math., Winnipeg, Man., 1979. MR0561043 (82b:10006)
%H A212908 Reinhard Zumkeller and Donovan Johnson, <a href="/A212908/b212908.txt">Table of n, a(n) for n = 1..2632</a> (terms up to a(2500) from Reinhard Zumkeller)
%t A212908 nmax = 258280326 (* = last term = a(2632) *);
%t A212908 kmax = 100 (* = number of terms to compute *);
%t A212908 a36288[n_] := a36288[n] = If[n==1, 1, Total[Times @@@ FactorInteger[n]]+1];
%t A212908 a212813[n_] := Module[{i, k = n}, For[i = 1, i <= 4, i++, If[k == 8, Return[i-1]]; k = a36288[k]]; -1];
%t A212908 k = 0;
%t A212908 Do[If[a212813[n] == 3, k++; If[k > kmax, Break[]]; a[k] = n; Print["a(", k, ") = ", n]], {n, 1, nmax}];
%t A212908 Array[a, kmax] (* _Jean-François Alcover_, Aug 02 2018 *)
%o A212908 (Haskell)
%o A212908 import Data.List (elemIndices)
%o A212908 a212908 n = a212908_list !! (n-1)
%o A212908 a212908_list = map (+ 1) $ elemIndices 3 a212813_list
%o A212908 -- _Reinhard Zumkeller_, May 30 2012
%Y A212908 Cf. A212813, A212814, A212815, A212816, A212909.
%K A212908 nonn,fini,full
%O A212908 1,1
%A A212908 _N. J. A. Sloane_, May 30 2012
%E A212908 Keyword "full" added by _Donovan Johnson_, Jun 02 2012