[seqfan] Re: Can anyone explain A206159?

[Neil Sloane]

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.
> %
>
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