OFFSET
1,1
COMMENTS
Largest prime factor of (10^(n+1)+1)*(10^n-1)/9.
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..344
FORMULA
EXAMPLE
a(4) = 9091 because largest prime factor of 111101111 is 9091.
MAPLE
seq(max(max(numtheory:-factorset((10^n-1)/9)),
max(numtheory:-factorset(10^(n+1)+1))), n=1..30); # Robert Israel, May 11 2016
PROG
(PARI) a006530(n) = if(n>1, vecmax(factor(n)[, 1]), 1);
for(n=1, 25, print1(a006530((10^(2*n+1)-1)/9-10^n), ", "));
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, May 11 2016
STATUS
approved