A103034 Numbers n such that 6*10^n + 4*R_n - 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 2, 7, 19, 25, 37, 49, 133, 613, 1340, 2036, 2491, 26263

Offset

1,3

Comments

Also numbers n such that (58*10^n-31)/9 is prime.

a(15) > 10^5. - Robert Price, Sep 10 2015

Links

Table of n, a(n) for n=1..14.

Makoto Kamada, Prime numbers of the form 644...441.

Index entries for primes involving repunits.

Formula

a(n) = A101527(n-1) + 1 for n>1.

Example

For n=0, (58*10^n-31)/9=3 which is prime, so 0 is the sequence.

Mathematica

Do[ If[ PrimeQ[(58*10^n - 31)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101527.

Sequence in context: A343908 A100408 A259370 * A038952 A144589 A179002

Adjacent sequences: A103031 A103032 A103033 * A103035 A103036 A103037

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

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

Inserted a(1)= 0 by Robert Price, Sep 10 2015

Status

approved