# [seqfan] Re: Two Sequences Related To Permutations of (1,2,...,n)

Leroy Quet q1qq2qqq3qqqq at yahoo.com
Sun Jan 18 14:51:15 CET 2009

```No, you don't misunderstand, I think.

I get that the sequence starts (offset = 1): 1,2,6,20,...,
which is definitely not a(n) = 2^(n-1).

Thanks,
Leroy Quet

--- On Sun, 1/18/09, Marc LeBrun <mlb at well.com> wrote:

> From: Marc LeBrun <mlb at well.com>
> Subject: [seqfan] Re: Two Sequences Related To Permutations of  (1,2,...,n)
> To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
> Date: Sunday, January 18, 2009, 6:21 AM
> >=Edwin Clark
>  >>=Leroy Quet
>  >> ...the entire set P of the n of these plotted
> points would be on
> the perimeter of the convex hull of P.
>  > Isn't this the same as permutations with exactly
> one local maximum.
>
> Maybe I misunderstand, but doesn't something like 1 8 2
> 9 3 4 5 6 7
> have 1. all points on the hull, but also 2. more than one
> local maximum?
>
> . . . x . . . . .
> . x . . . . . . .
> . . . . . . . . x
> . . . . . . . x .
> . . . . . . x . .
> . . . . . x . . .
> . . . . x . . . .
> . . x . . . . . .
> x . . . . . . . .
>
>
>
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```