

A101393


Numbers n such that 3*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,2


COMMENTS

Also numbers such that (28*10^n+53)/9 is prime.
All except 1, 2 and 218 only probably prime. No others less than 10000.


LINKS

Table of n, a(n) for n=1..8.
Makoto Kamada, Prime numbers of the form 311...117.
Index entries for primes involving repunits.


FORMULA

a(n) = A101826(n) + 1.


EXAMPLE

n = 1, 2 are members since 37 and 317 are primes.


MATHEMATICA

Do[ If[ PrimeQ[(28*10^n+53)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A100501, A100473, A101826.
Sequence in context: A125058 A202741 A239529 * A124188 A261936 A274466
Adjacent sequences: A101390 A101391 A101392 * A101394 A101395 A101396


KEYWORD

nonn


AUTHOR

Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005


EXTENSIONS

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


STATUS

approved



