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A103081
Numbers n such that 8*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
0, 3, 5, 101, 105, 4097, 5733, 9755, 31833
OFFSET
1,2
COMMENTS
Also numbers n such that (76*10^n+23)/9 is prime.
a(10) > 10^5. - Robert Price, Oct 18 2015
FORMULA
a(n) = A101068(n-1) + 1 for n>1.
MATHEMATICA
Do[ If[ PrimeQ[(76*10^n + 23)/9], Print[n]], {n, 0, 10000}]
PROG
(PARI) for(n=0, 1e5, if(isprime(k=(76*10^n+23)/9), print1(n", "))) \\ Altug Alkan, Oct 19 2015
CROSSREFS
Sequence in context: A173487 A279310 A364549 * A338269 A371194 A346710
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(9) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
Inserted a(1)=0 by Robert Price, Oct 18 2015
STATUS
approved