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A103067
Numbers n such that 7*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 4, 18, 28, 55, 1728, 1876, 1884, 6841, 10782, 25366, 98446, 137250
OFFSET
1,2
COMMENTS
Also numbers n such that (71*10^n+1)/9 is prime.
FORMULA
a(n) = A101153(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(71*10^n + 1)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A166749 A370406 A378633 * A080519 A120407 A033166
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(10)-a(13) from Kamada data by Robert Price, Dec 14 2010
STATUS
approved