OFFSET
1,1
COMMENTS
A prime p has 10 as a primitive root iff the length of the period of the decimal expansion of 1/p is p-1.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
test[p_] := MultiplicativeOrder[10, p]===p-1; Prime/@Select[Range[2, 800], test[Prime[ # ]]&&test[Prime[ #+1]]&&!test[Prime[ #-1]]&&!test[Prime[ #+2]]&]
Prime[#+1]&/@SequencePosition[Table[If[MultiplicativeOrder[10, p]===p-1, 1, 0], {p, Prime[Range[ 800]]}], {0, 1, 1, 0}][[;; , 1]] (* Harvey P. Dale, Nov 29 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jeff Burch, Mar 23 2001
EXTENSIONS
Edited by Dean Hickerson, Jun 17 2002
Offset corrected by Amiram Eldar, Oct 03 2021
STATUS
approved