OFFSET
1,2
COMMENTS
Numbers n such that 10^n + 8*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
a(21) > 10^5. - Robert Price, Nov 16 2014
a(24) > 2*10^5. - Robert Price, Jul 11 2015
LINKS
FORMULA
a(n) = A102034(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[2*10^n - 3], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=ispseudoprime(2*10^n-3) \\ Charles R Greathouse IV, Jun 06 2017
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 16 2004
EXTENSIONS
Addition of a(18)-a(20) from Kamada data by Robert Price, Dec 09 2010
a(21)-a(23) from Robert Price, Jul 11 2015
STATUS
approved