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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. 4
1, 1, 2, 6, 20, 80, 360, 1888, 11168, 75168, 560960, 4632320, 41627520, 405993472, 4256566784, 47855992320, 573443425280, 7304885964800, 98493107742720, 1402190308089856, 21008850635694080, 330557870033510400, 5448181151148032000, 93883859983130624000 (list; graph; refs; listen; history; text; internal format)
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: A150185 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

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Last modified March 30 12:10 EDT 2020. Contains 333125 sequences. (Running on oeis4.)