[seqfan] Re: Probable mistake in A013582 (number of states in Connect-4).

[Allan Wechsler]

The entry A013582 <https://oeis.org/A013582> has an ambiguity; it doesn't
say whether it is including positions that contain (a) *no* winning rows of
four (that is, only positions that have not yet been won), (b) *at most one
*row of four (that is, including some winning positions), (c) *any number *of
rows of four *as long as they are the same color and intersect in a single
cell that is at the top of its column *(that is, including all winning
positions), or (d) *with any number* of rows of four, unrestricted (that
is, including all positions that can be achieved simply by dropping in red
and blue chips alternately, ignoring winning conditions).

These four sequences would definitely be different, and all of
approximately equal interest; perhaps the entry should clarify exactly what
is being counted.

On Sat, Dec 3, 2022 at 5:14 PM Russ Cox <rsc at swtch.com> wrote:

> Hi Neil, Sean, Sidney,
>
> I got the sequence very wrong in 1996. (Sorry! I was a high school
> student.)
> Sean corrected it in 2018 and I wrote an independent program that agreed
> through a(15).
> Looks like Sean computed the later terms.
> I can't find my 2018 program at the moment - I should have uploaded it
> then.
> But I'm sure it was not able to get out to a(42), or I wouldn't have
> stopped at a(15).
> In any event, I will leave it to Sean and Sidney to work out the right
> terms.
>
> Best,
> Russ
>
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