[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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