

A177470


Avoiding the pattern 11'22'. To avoid 11'22' means not to have four consecutive letters such that the first letter is less than the third one and the second letter is less than the fourth one.


4



1, 1, 2, 6, 18, 70, 300, 1435, 7910, 47376, 316008, 2314158, 18331236, 158024724, 1462752720, 14497475850, 153488070450
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OFFSET

1,3


LINKS



PROG

(C) See Links section.


CROSSREFS



KEYWORD

nonn,more


AUTHOR

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


EXTENSIONS



STATUS

approved



