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A103022
Numbers n such that 5*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
3, 5, 6, 21, 309, 816, 858, 1115, 1419, 1689, 12009, 18693, 28098, 90965
OFFSET
1,1
COMMENTS
Also numbers n such that (53*10^n-71)/9 is prime.
a(15) > 10^5. - Robert Price, Sep 08 2015
FORMULA
a(n) = A101587(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(53*10^n - 71)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A295403 A272440 A276704 * A086189 A137082 A242501
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(11)-a(13) from Kamada data by Robert Price, Dec 13 2010
a(14) from Robert Price, Sep 08 2015
STATUS
approved