OFFSET
1,1
COMMENTS
The next term (a(13)) has 133 digits. - Harvey P. Dale, Jan 04 2023
LINKS
Sean A. Irvine, Table of n, a(n) for n = 1..13
EXAMPLE
2 is a term since all its consecutive digits differ by 5 (there aren't any).
19 is a term because 1 and 9 differ by 8.
23 is not a term because its consecutive digits differ only by 1.
MATHEMATICA
Module[{nn=500, nine, one}, one=Select[Table[FromDigits[PadRight[{}, n, {1, 9}]], {n, nn}], PrimeQ]; nine=Select[Table[FromDigits[PadRight[{}, n, {9, 1}]], {n, nn}], PrimeQ]; Sort[Join[{2, 3, 5, 7}, nine, one]]] (* Harvey P. Dale, Jan 04 2023 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Apr 15 1999
EXTENSIONS
Offset corrected by Sean A. Irvine, Jun 16 2021
STATUS
approved