A103098 Numbers n such that 9*10^n + 4*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

30, 41, 228, 581, 1290, 2580, 3696, 11390, 21558

Offset

1,1

Comments

Also numbers n such that (85*10^n-13)/9 is prime.

a(10) > 10^5. - Robert Price, Nov 05 2015

Links

Table of n, a(n) for n=1..9.

Makoto Kamada, Prime numbers of the form 944...443.

Index entries for primes involving repunits.

Formula

a(n) = A101007(n) + 1.

Mathematica

Do[ If[ PrimeQ[(85*10^n - 13)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101007.

Sequence in context: A043120 A039297 A043900 * A110849 A074696 A127663

Adjacent sequences: A103095 A103096 A103097 * A103099 A103100 A103101

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(8)-a(9) from Kamada data by Robert Price, Dec 14 2010

Status

approved