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A102997 Numbers n such that 4*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 463 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Also numbers n such that (44*10^n-71)/9 is prime.
No other terms below 10^5.
a(3) > 2*10^5. - Robert Price, Oct 15 2015
a(3) > 8*10^5, if it exists! - Robert Price, Dec 31 2016
LINKS
FORMULA
a(n) = A101734(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(44*10^n - 71)/9], Print[n]], {n, 10000}]
PROG
(PARI) for(n=0, 1000, if(isprime((44*10^n-71)/9), print1(n", "))) \\ Altug Alkan, Oct 15 2015
CROSSREFS
Sequence in context: A025038 A028684 A212928 * A252251 A139662 A140030
KEYWORD
bref,more,nonn
AUTHOR
Robert G. Wilson v, Jan 17 2005
STATUS
approved

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)