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A181047 Number of length-n sequences A over {1,2,3} with the property that all of r(A), r(r(A)), etc. are over {1,2,3}, where r is the sequence obtained by taking the run lengths in A. 0
1, 3, 9, 27, 54, 180, 426, 1080, 2724, 6300, 16512, 42432, 98064, 248256, 616656, 1509888, 3767040 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

EXAMPLE

For example, the run-lengths in 1333 are 13, then the run-lengths of this is 11, then the run-lengths of this is 2, then the run-lengths of this is 1, so this sequence is counted in a(4).

CROSSREFS

Sequence in context: A163791 A248078 A057829 * A014948 A093665 A093546

Adjacent sequences:  A181044 A181045 A181046 * A181048 A181049 A181050

KEYWORD

nonn,hard

AUTHOR

Jeffrey Shallit, Oct 01 2010

EXTENSIONS

a(0)-a(10) confirmed and a(11)-a(14) added by John W. Layman, Oct 07 2010

a(15)-a(16) from Alois P. Heinz, Oct 16 2011

STATUS

approved

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Last modified June 19 19:11 EDT 2019. Contains 324222 sequences. (Running on oeis4.)