

A102996


Numbers n such that 4*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,1


COMMENTS

Also numbers n such that (43*10^n+11)/9 is prime.
a(10) > 10^5.  Robert Price, Jun 01 2015


LINKS

Table of n, a(n) for n=1..9.
Makoto Kamada, Prime numbers of the form 477...779.
Index entries for primes involving repunits.


FORMULA

a(n) = A101733(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(43*10^n + 11)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101733.
Sequence in context: A218077 A240040 A088888 * A189896 A095182 A104465
Adjacent sequences: A102993 A102994 A102995 * A102997 A102998 A102999


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 17 2005


EXTENSIONS

a(8) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013
a(9) from Robert Price, Jun 01 2015


STATUS

approved



