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A103056 Numbers n such that 7*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 2, 5, 7, 85, 345, 1595, 2105, 6386, 9119, 9332, 14707, 72560 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Also numbers n such that (22*10^n+17)/3 is prime.
a(15) > 10^5. - Robert Price, Sep 26 2015
LINKS
FORMULA
a(n) = A101138(n-1) + 1 for n>1.
EXAMPLE
For n=0, (22*10^n+17)/3 = 13 which is a prime so 0 is a term.
MATHEMATICA
Do[ If[ PrimeQ[(22*10^n + 17)/3], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A293592 A042257 A343833 * A041445 A265815 A041961
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(13) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1) = 0 by Robert Price, Sep 26 2015
a(14) from Robert Price, Sep 26 2015
STATUS
approved

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Last modified June 19 17:03 EDT 2024. Contains 373504 sequences. (Running on oeis4.)