%I A087891
%S A087891 0,0,3,1,3,3,6,2,8,3,6,4,5,6,7,3,6,9,8,4,5,6,7,5,10,5,38,7,8,7,36,4,12,
%T A087891 6,7,10,9,8,12,5,37,5,13,7,9,7,36,6,11,11,10,6,7,39,40,8,14,8,12,8,9,36,
%U A087891 36,5,13,12,11,7,8,7,36,11,41,9,9,9,10,12,13,6,11,37,40,6,7,13,12,8,12
%N A087891 Number of non-square-free terms in 3x+1 trajectory started at n.
%e A087891 n=61: trajectory={61,184,92,46,23,70,35,...,20,10,5,16,8,4,2,1},
%e A087891 non-square-free terms={184,92,160,80,40,20,16,8,4}, so a(61)=9.
%t A087891 c[x_] := (1-Mod[x, 2])*(x/2)+Mod[x, 2]*(3*x+1); c[1]=1; fpl[x_] := Delete[FixedPointList[c, 
               x], -1] lf[x_] := Length[fpl[x]] Table[Count[Table[MoebiusMu[Part[fpl[w], 
               j]], {j, 1, lf[w]}], 0], {w, 1, 256}]
%Y A087891 Sequence in context: A085723 A165027 A078555 this_sequence A005885 A061892 
               A038573
%Y A087891 Adjacent sequences: A087888 A087889 A087890 this_sequence A087892 A087893 
               A087894
%K A087891 nonn
%O A087891 1,3
%A A087891 Labos E. (labos(AT)ana.sote.hu), Oct 02 2003