OFFSET
1,1
COMMENTS
Also numbers k such that (8*10^k + 1)/9 is prime.
a(15) > 2*10^5. - Robert Price, Sep 06 2014
LINKS
FORMULA
a(n) = A056663(n) + 1.
EXAMPLE
35 is a term because 88888888888888888888888888888888889 (34 8's) is a prime number.
MAPLE
select(n -> isprime((8*10^n+1)/9), [$1..10000]); # Robert Israel, Sep 07 2014
MATHEMATICA
Do[ If[ PrimeQ[ 8(10^n - 1)/9 + 1], Print[n]], {n, 0, 30000}] (* Robert G. Wilson v, Oct 15 2004 *)
PROG
(PARI)
for(n=1, 10^4, if(ispseudoprime(8*(10^n-1)/9+1), print1(n, ", "))) \\ Derek Orr, Sep 06 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jul 12 2004
EXTENSIONS
Four missing terms (9812, 12260, 12341, 13760) added, and a(12)-a(14) added from Kamada data, by Robert Price, Sep 06 2014
STATUS
approved