login
A103073
Numbers n such that 8*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 4, 7, 9, 19, 22, 70, 102, 121, 123, 235, 360, 594, 1614, 2410, 16048, 16174
OFFSET
1,2
COMMENTS
Also numbers n such that (73*10^n+71)/9 is prime.
a(18) > 10^5. - Robert Price, Oct 13 2015
FORMULA
a(n) = A101060(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(73*10^n + 71)/9], Print[n]], {n, 0, 10000}]
Select[Range[0, 100000], PrimeQ[(73 10^# + 71)/9] &] (* Vincenzo Librandi, Oct 14 2015 *)
PROG
(Magma) [n: n in [0..400] | IsPrime((73*10^n+71) div 9)]; // Vincenzo Librandi, Oct 14 2015
CROSSREFS
Sequence in context: A044903 A359016 A281144 * A166742 A346554 A022541
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(16)-a(17) from Kamada data by Robert Price, Dec 14 2010
STATUS
approved