[seqfan] Re: Numbers NOT of the form 2^x - y^2

[Frank Adams-Watters]

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.