A076229 Smallest number such that A076228(a(n)) = n.

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, 110, 118, 109, 114, 108, 199, 129, 146, 145, 188, 164, 278, 246, 265, 171, 195, 250, 193, 194, 216, 313, 430, 380, 429, 291, 257, 293, 290, 258, 639, 391, 411, 415, 572

Offset: 1

Author

Labos Elemer, Oct 01 2002

Keywords

• nonn

Examples

			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}.
		

Crossrefs

Cf. A006370, A074473, A076228.

Programs

Mathematica

f[x_] := (1-Mod[x,2])*(x/2)+(Mod[x,2])*(3*x+1); f[1]=1;
f0[x_] := Delete[FixedPointList[f,x],-1]
f1[x_] := f0[x]-Part[f0[x],1]
g[x_] := Count[Sign[f1[x]],-1]
t=Table[0,{256}]; Do[s=g[n]; If[s<257&&t[[s]]==0,t[[s]]=n],{n,1,1000}]; t

Formula

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