

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
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