# [seqfan] Re: Sum divides concatenation

zak seidov zakseidov at yahoo.com
Tue Sep 29 20:06:45 CEST 2009

```May be you mean a(n)>a(n-1)?
Otherwise,  why not a(4)=0:
1+2+6+0=9 and 9|1260?
Zak

--- On Tue, 9/29/09, John W. Layman <layman at math.vt.edu> wrote:

> From: John W. Layman <layman at math.vt.edu>
> Subject: [seqfan] Re: Sum divides concatenation
> To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
> Cc: Eric.Angelini at kntv.be
> Date: Tuesday, September 29, 2009, 12:28 PM
> Eric Angelini wrote:
> > Hello SeqFans,
> > I don't know how to find more terms -- thus I don't
> know
> > if this is old hat in Neil's database:
> >
> > 1, 2, 6, ...
> >
> > The sum of the first n integers divides the
> concatanion of
> > the first n integers; always prolong the seq with the
> smal-
> > lest _natural_ number not yet used:
> >
> > 1 divides 1  --> HIT
> > 1+2   (=3) divides 12 --> HIT
> > 1+2+3 (=6) does not divide 123
> > 1+2+4 (=7) does not divide 124
> > 1+2+5 (=8) does not divide 125
> > 1+2+6 (=9) divides 126 --> HIT
> > etc.
> >
> > Best,
> > É.
> >
> >
> >
>
> It takes Mathematica a couple of minutes to get
>     {1, 2, 6, 250488, 279786, 1060566, 1414088,
> 1767610, 2447460},
> which is not in the OEIS.
>
> Regards,
> John
>
>
>
>
> _______________________________________________
>
> Seqfan Mailing list - http://list.seqfan.eu/
>

```