

A099411


Numbers n such that 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


2



1, 2, 3, 6, 46, 394, 978, 2586, 2811, 2968, 3642, 4827, 4918, 5592, 5706, 10683, 12891, 14118, 74350, 88680
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OFFSET

1,2


COMMENTS

Also numbers n such that (10^n+11)/3 is prime.
a(21) > 10^5.  Robert Price, Nov 02 2014


LINKS

Table of n, a(n) for n=1..20.
Makoto Kamada, Prime numbers of the form 33...337.
Index entries for primes involving repunits


FORMULA

a(n) = A056680(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[ 3(10^n  1)/9 + 4], Print[n]], {n, 10000}]


CROSSREFS

Cf. A002275, A056680, A093168.
Sequence in context: A127315 A018359 A049383 * A018372 A097350 A062309
Adjacent sequences: A099408 A099409 A099410 * A099412 A099413 A099414


KEYWORD

hard,nonn


AUTHOR

Robert G. Wilson v, Oct 14 2004


EXTENSIONS

a(16)a(20) from Robert Price, Nov 02 2014


STATUS

approved



