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A103051
Numbers n such that 7*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 2, 4, 17, 25, 32, 50, 74, 173, 1724, 2084, 11398
OFFSET
1,2
COMMENTS
Also numbers n such that (64*10^n+71)/9 is prime.
a(13) > 10^5. - Robert Price, Sep 21 2015
FORMULA
a(n) = A101132(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(64*10^n + 71)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A006276 A318367 A317488 * A095018 A081356 A018269
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(12) from Kamada data by Robert Price, Dec 14 2010
STATUS
approved