A103077 Numbers n such that 8*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 5, 8, 14, 55, 103, 331, 1067, 13711, 24397, 54583

Offset

1,2

Comments

Also numbers n such that (74*10^n+61)/9 is prime.

a(13) > 10^5. - Robert Price, Oct 26 2015

Links

Table of n, a(n) for n=1..12.

Makoto Kamada, Prime numbers of the form 822...229.

Index entries for primes involving repunits.

Formula

a(n) = A101064(n) + 1.

Mathematica

Do[ If[ PrimeQ[(74*10^n + 61)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101064.

Sequence in context: A263235 A017988 A282444 * A090980 A329603 A309546

Adjacent sequences: A103074 A103075 A103076 * A103078 A103079 A103080

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(10)-a(11) from Kamada data by Robert Price, Dec 14 2010

a(12) from Robert Price, Oct 26 2015

Status

approved