A177475 Avoiding the pattern 131'2.To avoid 131'2 means not to have four consecutive letters such that if the third letter is removed, then in the obtained 3 letter word the smallest letter is the first one, and the largest letter is the second one.

1, 2, 6, 20, 81, 390, 2161, 13678, 96983

Offset

1,2

References

S. Kitaev, Introduction to partially ordered patterns, Discrete Applied Mathematics 155 (2007), 929-944.

Links

Table of n, a(n) for n=1..9.

S. Kitaev and A. Burstein, Introduction to partially ordered patterns.

Crossrefs

Sequence in context: A189839 A117574 A177481 * A118476 A260788 A337274

Adjacent sequences: A177472 A177473 A177474 * A177476 A177477 A177478

Keyword

nonn

Author

Signy Olafsdottir (signy06(AT)ru.is), May 09 2010

Status

approved