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A102957
Numbers n such that 2*10^n + 6*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
2
0, 1, 2, 4, 7, 14, 20, 39, 102, 156, 457, 1190, 2308, 5870, 8314, 9703, 12828, 14959, 17995, 19730, 26480, 31440
OFFSET
1,3
COMMENTS
Also numbers n such that (8*10^n+7)/3 is prime.
FORMULA
a(n) = A101965(n-1) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(8*10^n + 7)/3], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A108329 A057264 A045514 * A216898 A176450 A263345
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 17 2004
EXTENSIONS
Addition of a(17)-a(21) from Kamada data by Robert Price, Dec 10 2010
0 added by Arkadiusz Wesolowski, Mar 10 2011
a(22) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
STATUS
approved