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A103089
Numbers n such that 8*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
0, 5, 6, 185, 401, 480, 1319, 5646, 6029, 16824, 62387, 70638
OFFSET
1,2
COMMENTS
Also numbers n such that (79*10^n-61)/9 is prime.
a(13) > 10^5. - Robert Price, Oct 25 2015
FORMULA
a(n) = A101076(n+1) + 1, for n>1.
MATHEMATICA
Do[ If[ PrimeQ[(79*10^n - 61)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A041257 A337465 A041411 * A041601 A301648 A041827
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
1 more term. Next term exceeds 50000. Sean A. Irvine, Sep 10 2009
Inserted a(1)=0 and added a(11)-a(12) by Robert Price, Oct 25 2015
STATUS
approved