A177482 Suppose e<f, e<h, g<f and g<h. To avoid fegh means not to have four consecutive letters such that the second and the third letters are less than the first and the fourth letters.

1, 1, 2, 6, 20, 80, 360, 1888, 11168, 75168, 560960, 4632320, 41627520, 405993472, 4256566784, 47855992320, 573443425280, 7304885964800, 98493107742720, 1402190308089856, 21008850635694080, 330557870033510400, 5448181151148032000, 93883859983130624000

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..100

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

Crossrefs

Sequence in context: A357502 A187009 A144168 * A300011 A242154 A108124

Adjacent sequences: A177479 A177480 A177481 * A177483 A177484 A177485

Keyword

nonn

Author

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

Extensions

a(0)=1, a(10)-a(23) from Alois P. Heinz, Mar 10 2020

Status

approved