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
N. J. A. Sloane, Table of n, a(n) for n = 1..20000
Robert Dougherty-Bliss, Proof that A326894 is bounded with maximum value 20
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
KEYWORD
nonn,base
AUTHOR
Robert Dougherty-Bliss, Sep 13 2019
EXTENSIONS
Corrected by N. J. A. Sloane, Sep 13 2019
STATUS
approved