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A103094
Numbers n such that 9*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
5, 29, 60, 147, 186, 456, 678, 1373, 3378, 15726, 68231
OFFSET
1,1
COMMENTS
Also numbers n such that (83*10^n+7)/9 is prime.
a(12) > 10^5. - Robert Price, Oct 31 2015
FORMULA
a(n) = A101002(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(83*10^n + 7)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A177831 A115706 A031394 * A341083 A341085 A301858
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(10) from Kamada data by Robert Price, Dec 14 2010
a(11) from Robert Price, Oct 31 2015
STATUS
approved