# [seqfan] Re: permutation of nonnegative integers

Neil Sloane njasloane at gmail.com
Thu Apr 12 04:27:13 CEST 2018

```Of course they are of interest!  Roughly speaking if
it is worth discussing here it is worth including in the OEIS.

BTW, could you elaborate on "Increment a and b".  What exactly does that
mean?

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com

On Wed, Apr 11, 2018 at 12:47 PM, jnthn stdhr <jstdhr at gmail.com> wrote:

> Begin with a=0 and b=1 and include any of [a, a+b, a*b, b], in that order,
> not already in the sequence.  Increment a and b.  The sequence begins:
>
> 0, 1, 3, 2, 5, 6, 7, 12, 4, 9, 20, 11, 30, 13, 42, 15, 56, 8, 17, 72, 19,
> 90, 10, 21, 110, 23, 132, 25, 156, 27, 182, 14, 29, 210, 31,...
>
> If a(n) is prime and a(n+1) is an even number, we get:
>
> 6, 12, 30, 42, 72, 90, 132, 210, 240, 342, 420, 462, 552, 702, 870, 930,
> 1122, 1260, 1332, 1560, 1722, 1980, 2352, 2550, 2652,...
>
> which appears to be A024701 (a(n) = (-1 + prime(n+1)^2)/4.)
>
> Of interest?
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>

```