A102950 Numbers k such that 2*10^k + R_k + 8 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 223, 318, 427, 3727, 5227, 8779, 11383, 15415, 26382

Offset

1,2

Comments

Also numbers k such that (19*10^k + 71)/9 is prime.

a(11) > 10^5. - Robert Price, Feb 06 2015

Links

Table of n, a(n) for n=1..10.

Makoto Kamada, Prime numbers of the form 211...119.

Index entries for primes involving repunits.

Formula

a(n) = A101955(n) + 1.

Mathematica

Do[ If[ PrimeQ[(19*10^n + 71)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101955.

Sequence in context: A271799 A152824 A142386 * A143801 A118818 A142437

Adjacent sequences: A102947 A102948 A102949 * A102951 A102952 A102953

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

Addition of a(8)-a(10) from Kamada data by Robert Price, Dec 13 2010

Status

approved