A135401, A000898

[Maximilian Hasler]

I confirm my first hypothesis (that of being too tired)...
the sequence I give is the number of permutations satisfying the given
formula, but not necessarily self-inverse(?). Thus it should be an
upper bound, so I still don't understand why I get 70 where OEIS gives
76...
(but maybe I'll understand it in some hours or days...)
sorry for flooding your mailboxes....
M.H.

On Jan 20, 2008 11:44 AM, Maximilian Hasler <maximilian.hasler at gmail.com> wrote:
> I'm maybe a bit tired and miss something obvious, but the definition of
> http://www.research.att.com/~njas/sequences/A135401
> seems to indicate that one can simply choose any list of [n/2] numbers among
> {1...n} \ {(n+1)/2} for p(1)...p([n/2]) and the remaining values of p
> are given by
> the formula p(k) = n+1-p(n+1-k),
> This would mean
> A135401(n)=binomial(n\2*2,n\2)
> vector(20,n,A135401(n)) = [1, 2, 2, 6, 6, 20, 20, 70, 70, 252, 252,
> 924, 924, 3432, 3432, 12870, 12870, 48620, 48620, 184756]
>
> but instead of 70 there is 76 given in the current version.
>
> Maximilian
>
>
> On Jan 20, 2008 10:12 AM, Leroy Quet <q1qq2qqq3qqqq at yahoo.com> wrote:
> > Does A135401(n) = A000898(floor(n/2)), for n =
> > all positive integers?
> >
> > The rook problem on an n-by-n chessboard, as I
> > understand it, is directly connected to
> > permutations of (1,2,3,...n).
> > So maybe the connection between these two
> > sequences is obvious.
> >
> >
> > Thanks,
> > Leroy Quet
> >
> >
> >
> >
> >
> > \/\/\/\///////\\\\\\\/\/\/\/
> > /\/\/\///////**\\\\\\\/\/\/\
> > \/\/\///////*/\*\\\\\\\/\/\/
> > /\/\/\\\\\\\*\/*///////\/\/\
> > \/\/\/\\\\\\\**///////\/\/\/
> > /\/\/\/\\\\\\\///////\/\/\/\
> >
> >
> >       ____________________________________________________________________________________
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> >
> >
> >
>
>
>
> --
> Maximilian F. Hasler (Maximilian.Hasler(AT)gmail.com)
>



-- 
Maximilian F. Hasler (Maximilian.Hasler(AT)gmail.com)