[seqfan] Re: Divisors of the concatenation of n+1 and n

[Reinhard Zumkeller]

https://oeis.org/draft/A256285
Best
R.


2015-06-03 11:48 GMT+02:00 Eric Angelini <Eric.Angelini at kntv.be>:

> Hello SeqFans,
> t(n) is the smallest unused integer so far in T such that t(n) is a
> divisor of the concatenation of n+1 and n.
>
>      n =  1  2  3  4  5  6  7  8  9   10   11   12   13   14   15   16
>  17   18   19   20   21   22
> concat = 21 32 43 54 65 76 87 98 109 1110 1211 1312 1413 1514 1615 1716
> 1817 1918 2019 2120 2221 2322
>      T =  1, 2 43, 3, 5, 4,29, 7,109,  6,  173,  8,   9,  757, 17,  11,
> 23,  14,  673, 10, 2221, 18,...
>
> Example:
> The divisors of 1413 (concatenation of 14 and 13) are 1, 3, 9, 157, 471
> and 1413. As 1 and 3 appear already in T, we have t(13) = 9.
>
> Is T a permutation of the integers > 0 ?
>
> Best,
> É.
>
>
>
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