A103044 Numbers n such that 6*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 4, 10, 13, 178, 304, 331, 502, 744, 1027, 1770, 5305, 55075

Offset

1,2

Comments

Also numbers n such that (62*10^n-71)/9 is prime.

a(14) > 10^5. - Robert Price, Sep 15 2015

Links

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 688...881.

Index entries for primes involving repunits.

Formula

a(n) = A101537(n) + 1.

Mathematica

Do[ If[ PrimeQ[(62*10^n - 71)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101537.

Sequence in context: A032821 A101576 A179134 * A310360 A114719 A116954

Adjacent sequences: A103041 A103042 A103043 * A103045 A103046 A103047

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(13) from Robert Price, Sep 15 2015

Status

approved