[seqfan] Re: A000984
franktaw at netscape.net
franktaw at netscape.net
Wed May 7 20:22:03 CEST 2014
Just looking at this sequence. It seems like a lot of the comments are
just trivial restatements of 2n distinct objects, n each of two types.
Franklin T. Adams-Watters
-----Original Message-----
From: William Keith <william.keith at gmail.com>
To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
Sent: Wed, May 7, 2014 10:15 am
Subject: [seqfan] Re: A000984
That comment is wrong. The number of such words is the Catalan numbers,
A000108 -- for instance, a Dyck path is formed by using a for up steps
and
b for down steps. The condition that the b's never outnumber a's is
then
the condition that the path never goes below the horizontal.
William
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