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A103079
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, 26, 36, 38, 60, 80, 92, 174, 486, 627, 999, 1614, 4382, 4898, 8442, 17262, 17802, 35427, 40743
OFFSET
1,2
COMMENTS
Also numbers n such that (76*10^n-31)/9 is prime.
a(20) > 10^5. - Robert Price, Oct 20 2015
FORMULA
a(n) = A101066(n-1) + 1, for n>1.
MATHEMATICA
Do[ If[ PrimeQ[(76*10^n - 31)/9], Print[n]], {n, 0, 10000}]
PROG
(PARI) for(n=0, 1e3, if(isprime((76*10^n-31)/9), print1(n", "))) \\ Altug Alkan, Oct 20 2015
CROSSREFS
Sequence in context: A058763 A291158 A326733 * A046468 A138065 A240897
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(16)-a(19) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 by Robert Price, Oct 20 2015
STATUS
approved