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A103109 Numbers n such that 9*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 3, 4, 6, 9, 12, 16, 34, 129, 243, 252, 529, 4885, 6363, 12951, 13188, 29931, 34888, 49516, 67431, 77781 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Also numbers n such that (89*10^n-17)/9 is prime.
a(22) > 10^5. - Robert Price, Nov 14 2015
LINKS
FORMULA
a(n) = A101018(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(89*10^n - 17)/9], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=isprime(9*10^n + 8*(10^n-1)/9 - 1) \\ Anders Hellström, Nov 14 2015
CROSSREFS
Sequence in context: A202171 A182531 A097922 * A241639 A241655 A288346
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(15)-a(18) from Kamada data by Robert Price, Dec 14 2010
a(19) from Erik Branger May 01 2013 by Ray Chandler, Aug 17 2013
a(20)-a(21) from Robert Price, Nov 14 2015
STATUS
approved

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Last modified March 2 05:08 EST 2024. Contains 370460 sequences. (Running on oeis4.)