A076229 - OEIS

%I #12 Jan 11 2025 05:21:00

%S 2,3,5,7,6,9,20,12,14,19,22,41,18,55,28,33,37,58,36,50,59,65,57,66,78,

%T 110,118,109,114,108,199,129,146,145,188,164,278,246,265,171,195,250,

%U 193,194,216,313,430,380,429,291,257,293,290,258,639,391,411,415,572

%N Smallest number such that A076228(a(n)) = n.

%F a(n) = Min{x; A076228(x) = n}.

%e For n=6, a(6)=9 because first in iteration list starting with 9, i.e. in {9, 28, 14, 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1}, there are 6 terms below 9: {7, 5, 8, 4, 2, 1}.

%t f[x_] := (1-Mod[x,2])*(x/2)+(Mod[x,2])*(3*x+1); f[1]=1;

%t f0[x_] := Delete[FixedPointList[f,x],-1]

%t f1[x_] := f0[x]-Part[f0[x],1]

%t g[x_] := Count[Sign[f1[x]],-1]

%t t=Table[0,{256}]; Do[s=g[n]; If[s<257&&t[[s]]==0,t[[s]]=n],{n,1,1000}]; t

%Y Cf. A006370, A074473, A076228.

%K nonn

%O 1,1

%A _Labos Elemer_, Oct 01 2002