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A102977
Numbers n such that 3*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
0, 2, 3, 5, 6, 20, 776, 1185, 3164, 4212, 10733, 21726, 38235
OFFSET
1,2
COMMENTS
Also numbers n such that (34*10^n+11)/9 is prime.
a(14) > 10^5. - Robert Price, May 08 2015
FORMULA
a(n) = A101843(n-1) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(34*10^n + 11)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A109628 A192367 A227230 * A238335 A131599 A263650
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 17 2004
EXTENSIONS
Addition of a(11)-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
STATUS
approved