# [seqfan] Re: duplicate sequence related to set covering on a square grid

Neil Sloane njasloane at gmail.com
Wed Oct 2 05:48:25 CEST 2013

```Rob, Well caught!
Could one of the editors-in-chief merge them as A152125 and recycle A227112?
Thanks
Neil

On Tue, Oct 1, 2013 at 11:18 PM, Rob Pratt <Rob.Pratt at sas.com> wrote:

> It looks like:
>
> A227112<http://oeis.org/A227112>
>
> Given n^2 points forming a square grid, a(n) is the minimum number of
> points to be removed from the grid, so that, if 4 of the remaining ones are
> chosen, they do not form a square with sides parallel to the grid.
>
> +20
> 4
>
>
>
> 0, 1, 2, 4, 8, 12, 17, 23, 30, 39 (list<http://oeis.org/A227112/list>;
> graph<http://oeis.org/A227112/graph>; refs<
> http://oeis.org/search?q=A227112+-id:A227112>; listen<
> http://oeis.org/A227112/listen>; history<
> http://oeis.org/history?seq=A227112>; text<
> http://oeis.org/search?q=id:A227112&fmt=text>; internal format<
> http://oeis.org/A227112/internal>)
>
>
>
> is a newer and more complete version of:
>
> A152125<http://oeis.org/A152125>
>
> On a 4 X 4 square grid, there are 14 lattice squares parallel to the axes.
> What is the fewest dots you can remove from the grid such that at least one
> vertex of each of the 14 squares is removed? The answer is a(4) = 4. In
> general a(n) is the answer for an n X n grid.
>
> +20
> 0
>
>
>
> 0, 1, 2, 4, 8, 12, 17 (list<http://oeis.org/A152125/list>; graph<
> http://oeis.org/A152125/graph>; refs<
> http://oeis.org/search?q=A152125+-id:A152125>; listen<
> http://oeis.org/A152125/listen>; history<
> http://oeis.org/history?seq=A152125>; text<
> http://oeis.org/search?q=id:A152125&fmt=text>; internal format<
> http://oeis.org/A152125/internal>)
>
>
>
>
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>
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>

--
Dear Friends, I have now retired from AT&T. New coordinates:

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.