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A103042
Numbers n such that 6*10^n + 7*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
0, 2, 156, 1055, 1997, 8930, 9563, 19560, 26838, 63857
OFFSET
1,2
COMMENTS
Also numbers n such that (61*10^n-43)/9 is prime.
a(11) > 10^5. - Robert Price, Sep 12 2015
FORMULA
a(n) = A101535(n-1) + 1 for n>1.
MATHEMATICA
Do[ If[ PrimeQ[(61*10^n - 43)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A332585 A000725 A151614 * A284458 A260886 A142006
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
a(8)-a(9) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 by Robert Price, Sep 12 2015
a(10) from Robert Price, Sep 12 2015
STATUS
approved