# [seqfan] Re: Need help with graph sequences

wouter meeussen wouter.meeussen at pandora.be
Sat Feb 21 19:10:57 CET 2009

```Tanya,

I get

Table[Count[Map[cbs, ListGraphs[n]], False], {n,7}]
{0, 0, 1, 3, 16, 96, 812}
so it's not
A000271     1,0,0,1,3,16,96,675,5413

Wouter.

----- Original Message -----
From: "Tanya Khovanova" <mathoflove-seqfan at yahoo.com>
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Sent: Saturday, February 21, 2009 4:39 PM
Subject: [seqfan] Need help with graph sequences

>
> Hello SeqFans,
>
> I just submitted two sequences below. My inefficient program counts only
the first 6 terms. The problem is that the second sequence exists in the
OEIS, but I do not have any good reasons to believe that it is the same as
mine, I need the next term to make sure. Can you do that?
>
> %S A157015 1,2,3,8,18,60
> %N A157015 Number of graphs with n vertices, such that a bipartite
connected component exists.
> %C A157015 There exists a vertex which doesn't belong to a cycle of odd
length.
>
>
> %S A157016 0,0,1,3,16,96
> %N A157016 Number of graphs with n vertices such that a bipartite
connected component doesn't exist.
> %C A157016 Any vertex is connected to a cycle of odd length.
> %t A157016 cbs[g_] := Or @@ Map[BipartiteQ, Map[InduceSubgraph[g, #] &,
ConnectedComponents[g]]] Table[Count[Map[cbs, ListGraphs[n]], False], {n,
6}]
>
> Tanya
>
>
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```