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A103033
Numbers n such that 6*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 3, 4, 5, 6, 10, 13, 58, 96, 178, 360, 420, 455, 1008, 1517, 2975, 3999, 5425, 10819, 16036, 32076, 47237, 111385, 190935
OFFSET
1,2
COMMENTS
Also numbers n such that (19*10^n+11)/3 is prime.
a(25) > 3*10^5. - Robert Price, Oct 26 2023
FORMULA
a(n) = A101526(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(19*10^n + 11)/3], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A174057 A335231 A164977 * A099561 A110300 A143713
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(19)-a(20) from Kamada data by Robert Price, Dec 10 2010
a(21)-a(22) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(23)-a(24) from Robert Price, Oct 26 2023
STATUS
approved