# [seqfan] Re: A268539: Primes in

Bob Selcoe rselcoe at entouchonline.net
Thu Mar 3 04:21:11 CET 2016

```Hi Robert, Zak and Seqfans,

>>>Each term of A268539 is of the form (x^2-25)/48 = (x-5)(x+5)/48

Unless I'm mistaken, the values of x in Robert's equation are sequence A(x)
starting a(1)=5 with periodic first differences of [6,2,6,10], so A(x) =
5,11,13,19,29,35,37,43,53,59,61,67,77,83,85...

Might make for an interesting entry??

Cheers,
Bob Selcoe

--------------------------------------------------
From: <israel at math.ubc.ca>
Sent: Wednesday, March 02, 2016 7:56 PM
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Subject: [seqfan] Re: A268539: Primes in

> On Mar 2 2016, Zak Seidov wrote:
>
>> https://oeis.org/A268539
>>Are 2,3,7,17 the only primes in A268539?
>>
>>--
>>Seqfan Mailing list - http://list.seqfan.eu/
>>
>
> Yes.  Each term of A268539 is of the form (x^2-25)/48 = (x-5)(x+5)/48
> where x is an integer.  So if x > 53, it must factor...
>
> Cheers,
> Robert
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>
```