[seqfan] Re: Can anyone explain A206159?

Neil Sloane njasloane at gmail.com
Tue May 3 04:01:54 CEST 2022


I have edited A206159.  Harvey Dale discovered the errors when he computed
the sequence, so he gets full credit for that.  That should have been clear
from my message that started this discussion. The b-file was totally wrong,
so I deleted it. The incorrect comment about the nonprime terms was wrong
and distracting, so that has also gone. This whole business would have been
avoided if Reinhard had written his program in a language that was used by
more than 6 people.  It seems his program was correct, but I deleted it
anyway, since obviously no one had run it in ten years.

Best regards
Neil

Neil J. A. Sloane, Chairman, OEIS Foundation.
Also Visiting Scientist, Math. Dept., Rutgers University,
Email: njasloane at gmail.com



On Mon, May 2, 2022 at 8:33 PM Neil Sloane <njasloane at gmail.com> wrote:

> Thanks to everyone who responded!
>
> Harvey, it looks like the data is simply wrong.  So please go ahead and
> make the necessary corrections.  - And thanks for catching this error.
>
> Reinhart Zumkeller was an Editor-in-Chief for many years and contributed a
> great many sequences and comments.  He did not often make mistakes.
>
> Best regards
> Neil
>
> Neil J. A. Sloane, Chairman, OEIS Foundation.
> Also Visiting Scientist, Math. Dept., Rutgers University,
> Email: njasloane at gmail.com
>
>
>
> On Mon, May 2, 2022 at 8:14 PM <hv at crypt.org> wrote:
>
>> Neil Sloane <njasloane at gmail.com> wrote:
>> :Harvey Dale just asked me why the numbers 2, 3, 5, 7, 22, 55, and 77 (and
>> :lots of others)  are missing, and I am baffled.
>>
>> Part of the author's original submission was the Haskell program, which
>> based on my limited understanding appears to do what you'd expect - list
>> those n for which A095048(n) <= 2.
>>
>> I've installed ghc, a Haskell compiler and interpreter, and confirm
>> that the supplied program(s) give a different set of results that look
>> much more like you'd expect:
>>
>> > map a206159 [1..20]
>> [1,2,3,5,7,11,13,17,19,22,31,33,41,55,61,71,77,101,113,121]
>> >
>>
>> I can only assume that when preparing the submission the author pasted
>> in the output of some other function by mistake.
>>
>> Complete session is below, I can easily provide a longer list if desired.
>>
>> Hugo
>> ---
>> % ghci
>> GHCi, version 8.0.2: http://www.haskell.org/ghc/  :? for help
>> Prelude> import Data.List (group, sort)
>> Prelude Data.List> let a027750_row n = filter ((== 0) . (mod n)) [1..n]
>> Prelude Data.List> let a095048 = length . group . sort . concatMap show .
>> a027750_row
>> Prelude Data.List> let a206159_list = filter ((<= 2) . a095048) [1..]
>> Prelude Data.List> let a206159 n = a206159_list !! (n-1)
>> Prelude Data.List> map a206159 [1..20]
>> [1,2,3,5,7,11,13,17,19,22,31,33,41,55,61,71,77,101,113,121]
>> Prelude Data.List> ^D
>> Leaving GHCi.
>> %
>>
>> --
>> Seqfan Mailing list - http://list.seqfan.eu/
>>
>



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