A087263 a(n) is the least initial value of a 3x+1 trajectory in which n is the largest (peak) term or a(n) = 0 if n cannot be a peak value (i.e., when n = 2k+1, n = 4k+2, n = 16k+12, etc.).

1, 2, 0, 4, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 20, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0, 0, 32, 0, 0, 0, 0, 0, 0, 0, 13, 0, 0, 0, 0, 0, 0, 0, 48, 0, 0, 0, 7, 0, 0, 0, 56, 0, 0, 0, 0, 0, 0, 0, 21, 0, 0, 0, 68, 0, 0, 0, 72, 0, 0, 0, 0, 0, 0, 0, 80, 0, 0, 0, 84, 0, 0, 0, 19, 0, 0, 0, 0, 0, 0, 0, 96, 0, 0, 0

Offset

1,2

Links

Table of n, a(n) for n=1..99.

Mathematica

c[x_] := (1-Mod[x, 2])*(x/2)+Mod[x, 2]*(3*x+1); c[1]=1; fpl[x_] := Max[Delete[FixedPointList[c, x], -1]] t=Table[fpl[w], {w, 1, 15000}]; Table[Min[Flatten[Position[t, j]]], {j, 1, 256}]

Crossrefs

Cf. A025586.

Sequence in context: A243199 A305212 A104774 * A099894 A048298 A123565

Adjacent sequences: A087260 A087261 A087262 * A087264 A087265 A087266

Keyword

nonn

Author

Labos Elemer, Sep 11 2003

Status

approved