A103025 Numbers n such that 6*10^n-7 is prime.

1, 2, 5, 6, 7, 11, 17, 29, 42, 47, 96, 108, 166, 210, 331, 1022, 3593, 4426, 5704, 13936, 16486, 85910

Offset

1,2

Comments

Also numbers n such that 5*10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

a(23) > 2*10^5. - Robert Price, Aug 07 2015

Links

Table of n, a(n) for n=1..22.

Makoto Kamada, Prime numbers of the form 599...993.

Index entries for primes involving repunits.

Formula

a(n) = A101590(n) + 1.

Mathematica

Do[ If[ PrimeQ[6*10^n - 7], Print[n]], {n, 0, 10000}]

Prog

(PARI) is(n)=ispseudoprime(6*10^n-7) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A002275, A101590.

Sequence in context: A023699 A058605 A282183 * A134080 A342792 A111300

Adjacent sequences: A103022 A103023 A103024 * A103026 A103027 A103028

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

Addition of a(20)-a(22) from Kamada data by Robert Price, Dec 09 2010

Status

approved