A048405 Primes with consecutive digits that differ exactly by 8.

2, 3, 5, 7, 19, 191, 919, 919191919, 91919191919, 91919191919191919, 91919191919191919191919, 191919191919191919191919191919191

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

Cf. A048398, A048399, A048400, A048401, A048402, A048403, A048404, A048410.

Sequence in context: A117315 A158473 A048420 * A110457 A320584 A209191

Adjacent sequences: A048402 A048403 A048404 * A048406 A048407 A048408

Keyword

nonn,base

Author

Patrick De Geest, Apr 15 1999

Extensions

Offset corrected by Sean A. Irvine, Jun 16 2021

Status

approved