OFFSET
1,2
COMMENTS
Post's tag system maps a word w over {1,2} to w', where if w begins with 1, w' is obtained by appending 11 to w and deleting the first three letters, or if w begins with 2, w' is obtained by appending 2212 to w and deleting the first three letters.
We work over {1,2} rather than the official alphabet {0,1} because of the prohibition in the OEIS of terms (other than 0 itself) which begin with 0.
LINKS
Lars Blomberg, Table of n, a(n) for n = 1..8190 (For terms in A291797 up to length 36.)
Peter R. J. Asveld, On a Post's System of Tag. Bulletin of the EATCS 36 (1988), 96-102. See Table 3.
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 04 2017
EXTENSIONS
a(31)-a(71) from Lars Blomberg, Sep 08 2017
STATUS
approved