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A103010
Numbers k such that 5*10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
1
3, 5, 33, 48, 59, 60, 74, 126, 177, 228, 638, 1304, 1644, 2435, 4374, 8750, 15114, 16853, 30353, 30545, 36236
OFFSET
1,1
COMMENTS
Also numbers k such that (47*10^k + 43)/9 is prime.
a(22) > 10^5. - Robert Price, Jul 10 2015
FORMULA
a(n) = A101575(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(46*10^n + 43)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A235267 A284379 A372718 * A225866 A332704 A263295
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
a(17)-a(18) from Kamada data by Robert Price, Dec 14 2010
a(19)-a(21) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
STATUS
approved