login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A133235 Numerical encoding of a series of binary words generated by a recurrence - see comments. 2
22, 2222, 22211222, 22211222211222, 222112222112211222211222, 2221122221122112222112222112211222211222, 222112222112211222211222211221122221122112222112222112211222211222 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The sequence of words is bb, bbbb, bbbaabbb, bbbaabbbbaabbb, bbbaabbbbaabbaabbbbaabbb, ... given by the rule that the n-th word consists of the (n-1)st word, followed by the inverse of the (n-3)rd word, followed by the (n-1)st word.

Here a (or 1) and 2 (or b) represent the respective matrices

[1 1] [2 1]

[1 0] [1 0]

arising in the study of Markov numbers (A002559) - see link.

Question: Can this substitution-deletion system be described by a simple morphism of the type shown in A008352?

LINKS

Table of n, a(n) for n=0..6.

Tom Ace, Calculating Markoff numbers with matrices

EXAMPLE

a(4) = bbbaabbbbaabbaabbbbaabbb, a(2) = bbbaabbb, so a(5) = bbbaabbbbaabbaabbbbaabbb (bbbaabbb)^(-1) bbbaabbbbaabbaabbbbaabbb = bbbaabbbbaabbaabbbbaabbbbaabbaabbbbaabbb

CROSSREFS

Cf. A002559, A008352, A003849.

Sequence in context: A183488 A253128 A046445 * A114449 A069221 A069222

Adjacent sequences:  A133232 A133233 A133234 * A133236 A133237 A133238

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Oct 14 2007, based on an email message from James Propp, Jan 28 2005

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 6 16:34 EDT 2022. Contains 357270 sequences. (Running on oeis4.)