

A102956


Numbers n such that 2*10^n + 5*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 (23*10^n+31)/9 is prime.
a(9) > 10^5.  Robert Price, Feb 06 2015


LINKS

Table of n, a(n) for n=1..8.
Makoto Kamada, Prime numbers of the form 255...559.
Index entries for primes involving repunits.


FORMULA

a(n) = A101963(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(23*10^n + 31)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101963.
Sequence in context: A227704 A248405 A116341 * A031696 A005972 A082972
Adjacent sequences: A102953 A102954 A102955 * A102957 A102958 A102959


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Dec 17 2004


EXTENSIONS

Addition of a(7)a(8) from Kamada data by Robert Price, Dec 13 2010


STATUS

approved



