[seqfan] Re: 4xy + 6x - 1

[Olivier Gerard]

Youri,

If you restrict to x, y, 0 or positive integers,
your list is certainly 2 plus Mersenne primes,
anyway the next one should be 127.

If you allow x, y any integer, you will probably find
that only 2 cannot be represented this way.

Olivier


On Thu, Feb 19, 2015 at 3:55 PM, юрий герасимов <2stepan at rambler.ru> wrote:

>
> Dear SeqFans,
> Primes not of the form 4xy + 6x - 1: 2, 3, 7, 31, ...
>
> What in the next one?
>
> Thanks. JSG
>
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