A102966 Numbers n such that 3*10^n + 2*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 3, 6, 12, 408, 649, 949, 963, 1005, 2700, 19779, 22518, 22611, 40584, 55362, 70194

Offset

1,3

Comments

Also numbers n such that (29*10^n-11)/9 is prime.

a(18) > 10^5. - Robert Price, Apr 04 2015

Links

Table of n, a(n) for n=1..17.

Makoto Kamada, Prime numbers of the form 322...221.

Index entries for primes involving repunits.

Formula

a(n) = A101828(n-1) + 1.

Mathematica

Do[ If[ PrimeQ[(29*10^n-11)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101828.

Sequence in context: A139416 A013563 A009788 * A309719 A332365 A257276

Adjacent sequences: A102963 A102964 A102965 * A102967 A102968 A102969

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

Addition of a(12)-a(14) from Kamada data by Robert Price, Dec 13 2010

a(15) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(16)-a(17) from Robert Price, Apr 04 2015

Status

approved