OFFSET
0,4
LINKS
Pierre CAMI, Table of n, a(n) for n = 0..999
EXAMPLE
for n=0 1*(10^0)+1=2 prime so a(0)=1
for n=1 1*(10^1)+1=11 prime so a(1)=1
for n=2 1*(10^2)+1=101 prime so a(2)=1
for n=3 2*(10^3)-1=1999 prime so a(3)=2
MATHEMATICA
\Table[Module[{k=1}, While[NoneTrue[k 10^n+{1, -1}, PrimeQ], k++]; k], {n, 0, 90}] (* Harvey P. Dale, Jun 01 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Feb 05 2005
EXTENSIONS
Initial term of b-file corrected by N. J. A. Sloane, Aug 31 2009
Definition clarified by Harvey P. Dale, Jun 01 2022
STATUS
approved