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A103047
Numbers n such that 6*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
5, 57, 501, 515, 627, 641, 725, 53111, 65331, 109673
OFFSET
1,1
COMMENTS
Also numbers n such that (62*10^n+1)/9 is prime.
FORMULA
a(n) = A101540(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(62*10^n + 1)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A197558 A218658 A266278 * A223628 A107339 A139260
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
a(8)-a(10) from Kamada data by Robert Price, Dec 14 2010
STATUS
approved