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A103016
Numbers n such that 5*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 3, 4, 6, 10, 21, 30, 72, 199, 208, 270, 396, 619, 759, 1077, 1383, 1566, 1960, 2653, 3504, 3786, 6085, 13110, 36448, 39582, 47989, 50998, 66729
OFFSET
1,2
COMMENTS
Also numbers n such that (49*10^n+41)/9 is prime.
a(29) > 10^5. - Robert Price, Jul 21 2015
EXAMPLE
a(n) = A101581(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(49*10^n + 41)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A052548 A232268 A103049 * A061032 A091424 A092839
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(23) from Kamada data by Robert Price, Dec 09 2010
a(24)-a(26) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(27)-a(28) from Robert Price, Jul 21 2015
STATUS
approved