

A102995


Numbers n such that 4*10^n + 7*R_n  6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,2


COMMENTS

Also numbers n such that (43*10^n61)/9 is prime.
a(9) > 10^5.  Robert Price, Jun 01 2015


LINKS

Table of n, a(n) for n=1..8.
Makoto Kamada, Prime numbers of the form 477...771.
Index entries for primes involving repunits.


FORMULA

a(n) = A101732(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(43*10^n  61)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101732.
Sequence in context: A095696 A322930 A200575 * A211887 A041927 A041924
Adjacent sequences: A102992 A102993 A102994 * A102996 A102997 A102998


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 17 2005


EXTENSIONS

Two more PRP terms from Serge Batalov, Feb 15 2009
a(7)a(8) from Robert Price, Jun 01 2015


STATUS

approved



