[seqfan] Re: Another characterization of A244031?

M. F. Hasler seqfan at hasler.fr
Mon May 7 18:32:17 CEST 2018

On Sat, May 5, 2018 at 8:47 AM, David Wilson wrote:

> n such that 1 <= k^2 <= n   =>   n + k^2 is composite.

It's easy to see that this is completely equivalent, because y has to be
equal to 1 in order to have
x^2 + n y^2 strictly between n and 2n (and x^2 is never prime), so for the
considered purpose,
x^2 + n y^2 is equivalent to n + x^2.

The current definition is indeed a bit "obfuscated" (i.e. useless
and I'd be in favour of the proposed rephrasing.

- Maximilian

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