[seqfan] Re: Help with sequence

andrew at nevercenter.com andrew at nevercenter.com
Wed Aug 26 05:01:23 CEST 2009

To clarify a bit more, the "x" I'm referring to in the paragraph I've  
quoted below is the variable x in this equation

x^2 + n = y^2

The x values in these equations:

4x^2 + n = y^2
9x^2 + n = y^2

and so forth should read:

4x_1^2 + n = y^2
9x_2^2 + n = y^2

where x != x_1 != x_2, and so on.

     -Andrew Plewe-

Quoting andrew at nevercenter.com:

> By doing so we also find out information about the properties of x
> (indeed, 5 and 7 are divisors of allowable x values, while 2, 3, and 11
> are not). I haven't shown here how you can conclude this, but it's fairly
> trivial (it relates to the figurate nature of square numbers).
>     -Andrew Plewe-

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