OFFSET
1,2
COMMENTS
Next term is 22...2 (36 digits).
LINKS
Michel Marcus, Table of n, a(n) for n = 1..39
Patrick De Geest, Repdigits: WONplate 83
MATHEMATICA
a[n_]:=NestList[FromDigits[Append[{#}, n]]&, n, 34]; Union[Join[{1}, Flatten[Table[Select[a[n], PrimeQ[#+1]&], {n, 2, 8, 2}]]]] (* Jayanta Basu, May 30 2013 *)
Select[Flatten[Table[FromDigits[PadRight[{}, n, k]], {n, 40}, {k, 9}]], PrimeQ[ #+1]&] (* Harvey P. Dale, Apr 22 2018 *)
PROG
(PARI) u=30; for(n=1, u, r=(10^n-1)/9; for(a=1, 9, m=r*a; if(ispseudoprime(m+1), print1(m, ", ")))) \\ Michel Marcus, Jan 26 2023; after A028987
CROSSREFS
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
Offset corrected by Arkadiusz Wesolowski, Aug 14 2011
STATUS
approved