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A103103
Numbers n such that 9*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
3, 4, 5, 6, 8, 16, 34, 41, 52, 89, 105, 322, 635, 940, 944, 1131, 1198, 1743, 1872, 37914, 41656, 90096, 99474, 113468, 140337, 180432, 263523
OFFSET
1,1
COMMENTS
Also numbers n such that (29*10^n-17)/3 is prime.
a(28) > 3*10^5. - Robert Price, Sep 03 2019
FORMULA
a(n) = A101012(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(29*10^n - 17)/3], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A087743 A073568 A094576 * A217347 A249798 A037348
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(20)-a(21) from Kamada data by Robert Price, Dec 14 2010
a(22)-a(23) from Robert Price, Jan 10 2017
a(24)-a(26) from Robert Price, Sep 03 2019
a(27) from Robert Price, Jun 01 2023
STATUS
approved