A103012 Numbers n such that 5*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 47, 69, 99, 575, 715, 2179, 10541

Offset

1,3

Comments

Also numbers n such that (16*10^n+17)/3 is prime.

a(10) > 10^5. - Robert Price, Sep 08 2015

Links

Table of n, a(n) for n=1..9.

Makoto Kamada, Prime numbers of the form 533...339.

Index entries for primes involving repunits.

Formula

a(n) = A101577(n-1) + 1 for n>1.

Example

For n=0, (16*10^n+17)/3=11 which is prime, so 0 is in the sequence.

Mathematica

Do[ If[ PrimeQ[(16*10^n + 17)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101577.

Sequence in context: A245745 A023331 A187923 * A166958 A112056 A033231

Adjacent sequences: A103009 A103010 A103011 * A103013 A103014 A103015

Keyword

nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(9) from Kamada data by Robert Price, Dec 14 2010

Inserted a(1)=0 by Robert Price, Sep 08 2015

Status

approved