OFFSET
1,2
COMMENTS
Also numbers n such that 7*10^n + 9*R_n - 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
a(24) > 2*10^5. - Robert Price, Dec 19 2015
LINKS
FORMULA
a(n) = A101154(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[8*10^n - 9], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=ispseudoprime(8*10^n-9) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(22)-a(23) from Kamada data by Robert Price, Dec 14 2010
STATUS
approved