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A103019
Numbers n such that 5*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
2, 6, 9, 27, 30, 48, 141, 150, 372, 422, 1097, 3570, 4607, 5289, 10734, 11550, 32604, 42470, 46311, 67578
OFFSET
1,1
COMMENTS
Also numbers n such that (52*10^n-61)/9 is prime.
a(21) > 10^5. - Robert Price, Sep 05 2015
FORMULA
a(n) = A101584(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(52*10^n - 61)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A243558 A244427 A121624 * A101823 A242421 A093397
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(15)-a(16) from Kamada data by Robert Price, Dec 12 2010
a(17)-a(19) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(20) from Robert Price, Sep 05 2015
STATUS
approved