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 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 [ie when n=2k+1,n=4k+2,n=16k+12, etc.]. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS 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

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Last modified May 31 00:53 EDT 2020. Contains 334747 sequences. (Running on oeis4.)