OFFSET
0,3
COMMENTS
To avoid 121'3 means not to have four consecutive letters such that the first letter and the third one is less than the second, and the second one is less than and the fourth one.
LINKS
S. Kitaev, Introduction to partially ordered patterns, Discrete Applied Mathematics 155 (2007), 929-944. [WARNING: The sequence is erroneously given as 1, 2, 6, 20, 83, 411, ...]
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Oct 01 2024
STATUS
approved