OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..9
MATHEMATICA
Select[10^Range[3000]-9^Range[3000], PrimeQ]
PROG
(Magma) [ a: n in [0..400] | IsPrime(a) where a is 10^n-9^n ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Nov 21 2011
STATUS
approved