

A102992


Numbers n such that 4*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


3



1, 2, 4, 5, 13, 22, 25, 28, 38, 67, 142, 284, 295, 380, 397, 1217, 1640, 2885, 3286, 7735, 29306
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Also numbers n such that (41*10^n+13)/9 is prime.
a(22) > 10^5.  Robert Price, May 22 2015


LINKS

Table of n, a(n) for n=1..21.
Makoto Kamada, Prime numbers of the form 455...557.
Index entries for primes involving repunits.


FORMULA

a(n) = A101727(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(41*10^n + 13)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101727.
Sequence in context: A079407 A078652 A289491 * A273097 A232207 A136563
Adjacent sequences: A102989 A102990 A102991 * A102993 A102994 A102995


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 17 2005


EXTENSIONS

Addition of a(21) from Kamada data by Robert Price, Dec 09 2010


STATUS

approved



