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A102952
Numbers k such that 2*10^k + 4*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
1
2, 3, 6, 11, 30, 128, 183, 375, 2159, 2568, 3369, 24989, 38810, 59558, 74874
OFFSET
1,1
COMMENTS
Also numbers k such that (22*10^k - 31)/9 is prime.
a(16) > 10^5. - Robert Price, Apr 11 2015
FORMULA
a(n) = A101957(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(22*10^n - 31)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A324768 A086209 A022490 * A369223 A065653 A275783
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 17 2004
EXTENSIONS
Addition of a(12) from Kamada data by Robert Price, Dec 13 2010
a(13) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(14)-a(15) from Robert Price, Apr 11 2015
STATUS
approved