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A102990
Numbers n such that 4*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
2
2, 3, 6, 11, 15, 26, 28, 51, 150, 182, 228, 407, 638, 3581, 4125, 4983, 5666, 15890, 27743, 43362, 55367, 60744, 73701
OFFSET
1,1
COMMENTS
Also numbers n such that (13*10^n+17)/3 is prime.
a(24) > 10^5. - Robert Price, Jun 25 2015
FORMULA
a(n) = A101725(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(13*10^n + 17)/3], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A005211 A298702 A076307 * A351203 A138519 A138520
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 17 2005
EXTENSIONS
Addition of a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010
a(20) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013
a(21)-a(23) from Robert Price, Jun 25 2015
STATUS
approved