login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A326894 a(1) = 1; thereafter, a(n) is the reversal of the next prime after a(n - 1) in base 3 if n is prime, and the reversal of the next composite after a(n - 1) in base 3 if n is composite. 6
1, 2, 1, 4, 7, 8, 19, 20, 5, 2, 1, 4, 7, 8, 1, 4, 7, 8, 19, 20, 5, 2, 1, 4, 2, 4, 2, 4, 7, 8, 19, 20, 5, 2, 4, 2, 1, 4, 2, 4, 7, 8, 19, 20, 5, 2, 1, 4, 2, 4, 2, 4, 7, 8, 1, 4, 2, 4, 7, 8, 19, 20, 5, 2, 4, 2, 1, 4, 2, 4, 7, 8, 19, 20, 5, 2, 4, 2, 1, 4, 2, 4, 7, 8, 1, 4, 2, 4, 7, 8, 1, 4, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The sequence is written in base 10.
Rémy Sigrist's argument from A326344 gives an upper bound of 23, although the true maximum value is 20, as confirmed by Andrew Weimholt's argument from A326344.
LINKS
EXAMPLE
By definition, a(1) = 1. The next composite after a(3) = 1 is 4, or 11 in base 3. Reversed this is still 11 in base 3, or 4 in base 10. Thus a(4) = 4 since 4 is composite.
CROSSREFS
Sequence in context: A358566 A139769 A357470 * A275778 A007839 A364658
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
Corrected by N. J. A. Sloane, Sep 13 2019
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 13:51 EDT 2024. Contains 371914 sequences. (Running on oeis4.)