[seqfan] Re: A065843 and their crossrefs.

Neil Sloane njasloane at gmail.com
Sat Apr 23 18:06:51 CEST 2016

David, Yes, there does seem to be a problem with all those sequences!
It looks like they all need editing.
The definitions seem to be both incomplete and wrong

Could someone write a quick program to check A065843, A065844, etc?
Fix the base b (b=2 for A065843 (as David says, the present definition
seems wrong), b=3 for A065844, etc)
Fix n. Look at all words w of length n in base b. For each w, find
how many primes of length n you can get by permuting the digits of w. Then
a(n) = max over w of this number.

Best regards

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com

On Fri, Apr 22, 2016 at 7:49 PM, David Corneth <davidacorneth at gmail.com>

> I guess priority low.
> The sequences mentioned in the title are quite similar.
> A065843 has name
> 'Let u be any string of n digits from {0,...,2}; let f(u) = number of
> distinct primes, not beginning with 0, formed by permuting the digits of u;
> then a(n) = max_u f(u).'.
> The comment is about binary numbers. Should then the digits come from {0,
> 1}? If so then I guess this sequence and the 10 crossrefs in it should be
> edited at some  point to fix it. I could do it but I can only have 7 drafts
> at a time and I have 3 other drafts already. Should these edits be made?
> Furthermore, for A065843, I'd write the example as
> 'a(4)=2 because 1011 and 1101 in base-2-notation are primes. No other set
> of four-digit-numbers in binary with the same digitsum have the same number
> of primes in them.'
> Could some-one enlighten my here?
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