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A100473
Numbers k such that 9*10^k + R_k + 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
2
1, 17, 23, 73, 131, 473, 685, 701, 1909, 3029, 3473, 4193, 9931
OFFSET
1,2
COMMENTS
Also numbers k such that (82*10^k + 53)/9 is a prime.
Some of the larger entries may only correspond to probable primes.
a(14) > 10^5. - Robert Price, Oct 25 2015
FORMULA
a(n) = A100999(n) + 1.
EXAMPLE
n = 1, 17, so that 97 and 911111111111111117 are primes.
MATHEMATICA
Do[ If[ PrimeQ[(82*10^n + 53)/9], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Jan 19 2005 *)
CROSSREFS
Sequence in context: A043142 A043922 A260179 * A060252 A127924 A250640
KEYWORD
more,nonn
AUTHOR
Julien Peter Benney (jpbenney(AT)ftml.net), Nov 21 2004
EXTENSIONS
a(8)-a(12) from Robert G. Wilson v, Jan 12 2005
a(13) from Robert G. Wilson v, Jan 12 2005
STATUS
approved