[seqfan] Re: Number Of Such Permutations

[Ivica Kolar]

Hello Leroy,
I do not know do you need it or not, however...
Checking my old notes I've found two more terms for A099152,
for n=14, 15 it is:
367854835,  3622508685
--ivica

----- Original Message ----- 
From: "Leroy Quet" <q1qq2qqq3qqqq at yahoo.com>
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Sent: Tuesday, January 05, 2010 9:38 PM
Subject: [seqfan] Re: Number Of Such Permutations


> Thanks, Rob.
>
> I myself SHOULD have plugged in the terms I had, with 24 replaced with 23; 
> then tried 24 replaced with 25 if that didn't give anything, since there 
> was a significant chance I erred by 1 or by some small integer.
>
> I would have seen the sequence I needed right off if I bothered to read 
> the comments to the dozens of sequences that match 1,1,3,7,23.
>
> Live and learn.
>
> Thanks,
> Leroy Quet
>
> [ ( [ ([( [ ( ([[o0Oo0Ooo0Oo(0)oO0ooO0oO0o]]) ) ] )]) ] ) ]
>
>
> --- On Tue, 1/5/10, Rob Pratt <Rob.Pratt at sas.com> wrote:
>
>> From: Rob Pratt <Rob.Pratt at sas.com>
>> Subject: [seqfan] Re: Number Of Such Permutations
>> To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>, 
>> "seqfan at seqfan.eu" <seqfan at seqfan.eu>
>> Date: Tuesday, January 5, 2010, 4:46 PM
>> I get a(5) = 23, and the sequence
>> seems to be:
>> http://www.research.att.com/~njas/sequences/A099152
>>
>> Rob Pratt
>>
>> -----Original Message-----
>> From: seqfan-bounces at list.seqfan.eu
>> [mailto:seqfan-bounces at list.seqfan.eu]
>> On Behalf Of Leroy Quet
>> Sent: Tuesday, January 05, 2010 11:13 AM
>> To: seqfan at seqfan.eu
>> Subject: [seqfan] Number Of Such Permutations
>>
>> This email will expose my ignorance, I am sure.
>>
>> Let P = (p(1),p(2),p(3),...,p(n)) be a permutation of
>> (1,2,3,...,n).
>>
>> How many of these permutations, for a given n, are there
>> such that for every p(m) equal to k, p(m+j) does not equal
>> k+j, for j equal any positive integer, and for all k between
>> 1 and n?
>>
>> For instance, for n = 4, we count these permutations:
>> 2413
>> 4213
>> 4132
>> 4321
>> 2431
>> 3241
>> 3142
>>
>> But we would not count, for instance, this permutation:
>> 1432
>> Because 1+2 = 3 is at a position two to the right of 1.
>>
>> I get (by hand, so very likely erroneously) the sequence of
>> number of permutations starting (first term is a(1)):
>> 1,1,3,7,24
>>
>> Searching this with the word "permutations" brings up no
>> hits.
>> Did I calculate these terms of the sequence correctly?
>>
>> Is this sequence in the OEIS as something else not
>> obviously related to permutations, perhaps?
>>
>> Sorry about my ignorance.
>>
>> Thanks,
>> Leroy Quet
>>
>>
>> [ ( [ ([( [ ( ([[o0Oo0Ooo0Oo(0)oO0ooO0oO0o]]) ) ] )]) ] )
>> ]
>>
>>
>>
>>
>>
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