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A102930
Numbers k such that 10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
2
1, 2, 4, 14, 25, 32, 56, 62, 811, 812, 1084, 2533, 11924, 49552
OFFSET
1,2
COMMENTS
Also numbers k such that (11*10^k + 43)/9 is prime.
a(15) > 10^5. - Robert Price, Jan 16 2015
a(15) > 2*10^5. - Tyler Busby, Feb 01 2023
FORMULA
a(n) = A102010(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(11*10^n + 43)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A350050 A096012 A261562 * A357996 A135113 A050564
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 16 2004
EXTENSIONS
Addition of a(13) from Kamada data by Robert Price, Dec 12 2010
a(14) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
STATUS
approved