# [seqfan] Re: A259444

APPLEGATE, DAVID L (DAVID L) david at research.att.com
Sun Oct 25 17:43:04 CET 2015

```Perhaps because 4 has not occurred as an earlier term, so 4^2 (and 2^4) are not forbidden values.  Only exponentials using values already in the sequence are forbidden.
-Dave

-----Original Message-----
From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Hans Havermann
Sent: Sunday, October 25, 2015 12:33 PM
To: Sequence Fanatics Discussion list
Subject: [seqfan] Re: A259444

Can you example what comes after 15? Why is 4^2 not avoided? More specifically, how is the sequence different from A007916 (which avoids 16)?

> On Oct 25, 2015, at 11:54 AM, Neil Sloane <njasloane at gmail.com> wrote:
>
> 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

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