# [seqfan] Re: A259444

Neil Sloane njasloane at gmail.com
Sun Oct 25 16:54:54 CET 2015

```It looks like ^ is exponentation, which is what it always is

After 2, we have to avoid 2^2 = 4, so 3 works

After 2,3 we have to avoid 2^2=4, 2^3=8, 3^2=9, 3^3=27, so 5 works,
also 6, also 7. Then 10, 11 and so on

I will add some examples to the sequence

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.
Email: njasloane at gmail.com

On Sun, Oct 25, 2015 at 10:58 AM, Vladimir Shevelev <shevelev at bgu.ac.il>
wrote:

> I do not understand the definition of A259444:
> "a(1)=2. For n>1, a(n) = smallest number > a(n-1)
> such that, for all m,r<n, a(n) != a(m)^a(r)."
> The first terms 2, 3, 5, 6, 7, 10,...
>
> Most likely, the author meant under ^ another operation.
> But + is not suitable: indeed, if a(n) != a(m)+a(r), then
> a(6)=10 is not suitable, since for m=2, r=5 we have a(m)+a(r)=a(6)
> and also for m=3, r=3 we also have a(m)+a(r)=a(6).
> What is the right definition?
>
> Best regards,