[seqfan] Re: Non-collinear permutations

[franktaw at netscape.net]

The title is fine, in my opinion, but I think at least one if not both 
of those (your first two paragraphs) should be included as comments. It 
may be obvious to you, but it isn't to the casual reader. I think the 
base target audience for the OEIS is a person with an undergraduate 
degree in mathematics, or a scientist dealing with mathematics in his 
work. I don't think either of those would immediately understand 
"permutation with no 3 points collinear".

Franklin T. Adams-Watters

-----Original Message-----
From: Ron Hardin <rhhardin at att.net>

Number of permutations of 1..n with no three points (i,p(i)) (j,p(j)) 
(k,p(k))
collinear.

Number of nXn permutation matrices with no three 1's collinear.

Better wording?  Specificity seems to introduce too much machinery.

E.g., 1,2,3  and 3,2,1 seem to cry out collinear on their own.

 rhhardin at mindspring.com
rhhardin at att.net (either)



----- Original Message ----
> From: "franktaw at netscape.net" <franktaw at netscape.net>
> To: seqfan at list.seqfan.eu
> Sent: Mon, June 21, 2010 1:48:11 PM
> Subject: [seqfan] Re: Non-collinear permutations
>
> I assume that you mean that no three points of the form (n,p(n)) are
> collinear. You should clarify this in a comment.

Franklin T.
> Adams-Watters