

A102954


Numbers n such that 2*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



3, 9, 15, 21, 27, 87, 180, 1941, 3960, 4995, 8577, 23481, 27855, 80595
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OFFSET

1,1


COMMENTS

Also numbers n such that (22*10^n+23)/9 is prime.
a(15) > 10^5.  Robert Price, Mar 15 2015


LINKS

Table of n, a(n) for n=1..14.
Makoto Kamada, Prime numbers of the form 244...447.
Index entries for primes involving repunits.


FORMULA

a(n) = A101959() + 1.


MATHEMATICA

Do[ If[ PrimeQ[(22*10^n + 23)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101959.
Sequence in context: A222640 A110108 A162843 * A272749 A273560 A246388
Adjacent sequences: A102951 A102952 A102953 * A102955 A102956 A102957


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Dec 17 2004


EXTENSIONS

Addition of a(12)a(13) from Kamada data by Robert Price, Dec 12 2010
a(14) from Robert Price, Mar 15 2015


STATUS

approved



