

A102942


Numbers n such that 10^n + 7*R_n  4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,2


COMMENTS

Also numbers n such that (16*10^n43)/9 is prime.
a(11) > 10^5.  Robert Price, Feb 11 2015


LINKS

Table of n, a(n) for n=1..10.
Makoto Kamada, Prime numbers of the form 177...773.
Index entries for primes involving repunits.


FORMULA

a(n) = A102027(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(16*10^n  43)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A102027.
Sequence in context: A150673 A242747 A195585 * A212691 A206803 A212527
Adjacent sequences: A102939 A102940 A102941 * A102943 A102944 A102945


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Dec 16 2004


EXTENSIONS

a(10) from Robert Price, Feb 11 2015


STATUS

approved



