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A103027
Numbers n such that 6*10^n + R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
2, 3, 5, 11, 12, 23, 75, 101, 122, 173, 647, 2015, 2684, 11700, 19625
OFFSET
1,1
COMMENTS
Also numbers n such that (55*10^n+17)/9 is prime.
a(16) > 10^5 - Robert Price, Sep 09 2015
FORMULA
a(n) = A101519(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(55*10^n + 17)/9], Print[n]], {n, 0, 10000}]
Select[Range[0, 10000], PrimeQ[(55 10^# + 17)/9] &] (* Vincenzo Librandi, Sep 10 2015 *)
PROG
(Magma) [n: n in [0..500]| IsPrime((55*10^n + 17) div 9)]; // Vincenzo Librandi, Sep 10 2015
CROSSREFS
Sequence in context: A066159 A316794 A372009 * A093902 A269004 A100475
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(14)-a(15) from Kamada data by Robert Price, Dec 12 2010
STATUS
approved