A087253 Number of distinct initial values of various 3x+1 trajectories of which the peak-value equals 4n.

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

Author

Labos Elemer, Sep 08 2003

Keywords

• nonn

Examples

			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.