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A102955
Numbers n such that 2*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 15, 31, 73, 97, 499, 4207, 5902, 9568, 12142, 13048, 38341, 80167, 91903
OFFSET
1,2
COMMENTS
Also numbers n such that (22*10^n+41)/9 is prime.
a(15) > 10^5. - Robert Price, Feb 05 2015
FORMULA
a(n) = A101960(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(22*10^n + 41)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A195046 A324631 A346897 * A041444 A041446 A042853
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 17 2004
EXTENSIONS
Addition of a(10)-a(11) from Kamada data by Robert Price, Dec 13 2010
a(12) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(13)-a(14) from Robert Price, Feb 05 2015
STATUS
approved