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A103030 Numbers n such that 6*10^n + 2*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 3, 7, 16, 39, 229, 352, 433, 766, 2887, 2976, 10836, 15097 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Also numbers n such that (56*10^n-11)/9 is prime.
a(15) > 10^5. - Robert Price, Sep 08 2015
LINKS
FORMULA
a(n) = A101522(n-1) + 1.
EXAMPLE
For n=0, (56*10^n-11)/9 = 5 which is prime, so 0 is in the sequence.
MATHEMATICA
Do[ If[ PrimeQ[(56*10^n - 11)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A271788 A103439 A147321 * A263316 A001698 A261236
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(13)-a(14) from Kamada data by Robert Price, Dec 13 2010
Inserted a(1)=0 by Robert Price, Sep 08 2015
STATUS
approved

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Last modified March 19 02:49 EDT 2024. Contains 370952 sequences. (Running on oeis4.)