login
A102960
Numbers n such that 2*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
2, 12, 27, 44, 80, 119, 131, 275, 315, 876, 1307, 10895, 17105, 60717
OFFSET
1,1
COMMENTS
Also numbers n such that (26*10^n-71)/9 is prime.
a(15) > 10^5. - Robert Price, Mar 16 2015
FORMULA
a(n) = A101969(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(26*10^n - 71)/9], Print[n]], {n, 10000}]
CROSSREFS
Sequence in context: A152811 A294552 A294170 * A166151 A154149 A354780
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 17 2004
EXTENSIONS
Addition of a(12)-a(13) from Kamada data by Robert Price, Dec 13 2010
a(14) from Robert Price, Mar 16 2015
Erroneous zero term deleted by Robert Price, Mar 17 2015
STATUS
approved