[seqfan] Re: Numbers NOT of the form 2^x - y^2
charles.greathouse at case.edu
Tue Oct 7 16:34:59 CEST 2014
Is there a number n such that A200522(n) = 0 but n is not in A051213? That
is, are modular restrictions the only obstacle to membership?
Case Western Reserve University
On Tue, Oct 7, 2014 at 1:26 AM, Frank Adams-Watters <franktaw at netscape.net>
> A200522 appears to be the answer.
> Franklin T. Adams-Watters
> -----Original Message-----
> From: Alonso Del Arte <alonso.delarte at gmail.com>
> To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> Sent: Mon, Oct 6, 2014 11:38 pm
> Subject: [seqfan] Numbers NOT of the form 2^x - y^2
> A sequence from Juri-Stepan raises for me a question I find very
> interesting: how can you be absolutely sure a number is NOT of the form 2^x
> - y^2 ? The answer would also be relevant for the supersequence, A051213.
> Since Juri's subsequence consists of the prime numbers of the form, I had
> the foggy notion that Legendre's symbol is relevant, but I can't figure out
> if I'm on the right track with that.
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