# [seqfan] Re: sparse odd entries

David Wilson davidwwilson at comcast.net
Tue Apr 18 02:44:40 CEST 2017

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> -----Original Message-----
> From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Peter
> Munn
> Sent: Monday, April 17, 2017 7:07 AM
> To: Sequence Fanatics Discussion list
> Subject: [seqfan] Re: sparse odd entries
>
> On Thu, 13 April, 2017 8:25 pm, David Newman wrote:
> > I'm looking for sequences which have few entries which are odd.
> > A117958 which has a(n) congruent to 1 (mod 2) only for n=m squared,
> > and m not divisible by 3 is an example of what I'm looking for. Is
> > there some easy way to search for such sequences?
>
> Hi David,
>
> The only thing I can add to the answers of others is that searching for
> comments seems to yield a high density of suitable sequences with
> well-chosen search terms.  The numbers quoted below, though, are the total
> number of search results:
>
> "most terms are even" gives 2
> "few odd terms" gives 3
> "first odd term" gives 18
> "only odd term" gives 19
> "last odd term" gives 9
> "smallest odd term" gives 3
> "largest odd term" gives 4
> "known odd terms" gives 1
> "rare odd" gives 1
>
> Sometimes the density of good results is much improved by specifying that
> the search apply to the comments only, for example:
>
> [comment:"first odd number"] gives 12
> [comment:"last odd number"] gives 10
>
> Combining a search for comments with a search on the sequence terms can
> work even better.  The following seems to have many good examples
> amongst
> its list:
>
> [comment:"odd term" 2 4 8 -seq:3 -seq:5 -seq:7 -seq:9 -seq:11 -seq:13]
> gives 43
>
> Best Regards,
>
> Peter
>
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/

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