OFFSET
1,1
COMMENTS
a(n) is always an n digit number.
Note that if distinct primes are required, the only change is that a(1) = 3.
LINKS
Hans Havermann, Table of n, a(n) for n = 1..50
FORMULA
10^n - a(n) is prime.
EXAMPLE
10^1=5+5; 10^2=47+53; 10^3=491+509;
10^4=4919+5081; 10^5=49877=50123; 10^6=499943+500057;
10^7=4999913+5000087; 10^8=49999757+50000243;
10^9=499999931+500000069;
10^10=4999999937+5000000063; etc.
MATHEMATICA
Table[ h =10^n/2; c=0; While[ PrimeQ[ h-c ]==False || PrimeQ[ h+c ]==False, c++ ]; h-c, {n, 1, 50} ] (from Hans Havermann, Nov 02 2006)
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Zak Seidov, Nov 02 2006
EXTENSIONS
Edited by N. J. A. Sloane May 15 2008 at the suggestion of R. J. Mathar.
STATUS
approved