login
A087253
Number of distinct initial values of various 3x+1 trajectories of which the peak-value equals 4n.
2
1, 1, 0, 6, 1, 1, 0, 1, 0, 3, 0, 1, 12, 1, 0, 3, 1, 1, 0, 1, 1, 8, 0, 1, 3, 1, 0, 3, 1, 0, 0, 1, 1, 3, 0, 1, 3, 1, 0, 13, 0, 1, 0, 1, 1, 3, 0, 1, 8, 1, 0, 3, 1, 0, 0, 1, 1, 6, 0, 1, 3, 0, 0, 3, 1, 1, 0, 1, 1, 3, 0, 1, 0, 1, 0, 14, 1, 1, 0, 1, 1, 0, 0, 1, 6, 1, 0, 3, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 3, 1, 1, 0, 1, 0
OFFSET
1,4
EXAMPLE
n=13: a(13)=12 because peak=4.13=52
occurs at the following 12 initial values:
{7,9,11,14,17,18,22,28,34,36,44,52};
this list differs from trajectory started at iv=52.
Impossible peaks of 4k form are listed in A087252
(corresponding to a[x]=0).
CROSSREFS
Cf. A025586.
Sequence in context: A114153 A119832 A166141 * A197686 A331277 A369458
KEYWORD
nonn
AUTHOR
Labos Elemer, Sep 08 2003
STATUS
approved