[seqfan] Re: Nice new sequence with interesting open problem

[rgwv at rgwv.com]

Something is wrong with this sequence. 2 cannot follow 1. The definition requires that 4 follow 1. Bob.

-----Original Message-----
From: SeqFan <seqfan-bounces at list.seqfan.eu> On Behalf Of Neil Sloane
Sent: Thursday, September 12, 2019 1:20 PM
To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
Subject: [seqfan] Nice new sequence with interesting open problem

Sent in by Max Tohline

A326344 a(1) = 1. Thereafter, if n is prime, a(n) is the next prime after a(n-1), but written backwards. If n is not prime, a(n) is the next composite after a(n-1), written backwards.


1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 4, 5, 6, 8, 9, 11, 21, 32, 33, 43, 44, 74, 57, 85, 68, 96, 89, 79, 8, 11, 21, 22, 42, 44, 54, 95, 69, 7, 8, 11, 21, 32, 33, 43, 44, 74, 57, 85, 68, 96, 89, 79, 8, 9, 1, 4, 6, 7, 8, 11, 21, 22, 42, 44, 54, 95, 69, 7, 8, 11, 21, ...


It appears that this does not exceed 909, reached for the first time at n =
21752

Michel Marcus checked it up to 10^8.

It would be nice to know more!

The record high values are:

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 21, 32, 33, 43, 44, 74, 85, 96, 97, 98, 99, 101, 201, 202, 302, 703, 804, 806, 807, 808, 907, 908, 909 (as far as they are known, see A326298, A326402)

Neil

--
Seqfan Mailing list - http://list.seqfan.eu/


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus