[seqfan] Re: Sum avoidance on a decimal string

[Neil Sloane]

That's very confusing!
"Form a string K by concatenating the ordered set of Natural numbers from 1
to infinity.  Then a(n) is the least x > a(n-1) where x does not equal
Sum{a_i..a_j} a_i, for i >= 1; with a_i some single digit in K, and with n
>= j-i."
Could you explain in detail how a(1), a(2), a(3) say are calculated? The
recursive summation Sum{a_i..a_j} a_i
is new to me!

Best regards
Neil

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 Thu, Sep 26, 2019 at 5:00 AM Christopher Hohl via SeqFan <
seqfan at list.seqfan.eu> wrote:

> Hi seqfans!
> Form a string K by concatenating the ordered set of Natural numbers from 1
> to infinity.  Then a(n) is the least x > a(n-1) where x does not equal
> Sum{a_i..a_j} a_i, for i >= 1; with a_i some single digit in K, and with n
> >= j-i.
> The first twelve entries (done on paper) are the following;
> 2,4,7,8,11,13,16,17,19,23,29,50,...
> Fairly 'odious' to start, but quite quickly things run amok.
> Looking for help computing much higher terms, if anyone has the interest-
> or the time.
> Although it is a fair impossibility, here's hoping everyone is well!
>                 ~ Christopher Hohl
> Sent from Yahoo Mail on Android
>
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