A102983 Numbers n such that 4*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 5, 77, 206, 1871, 3887, 11582, 20234, 60290

Offset

1,1

Comments

Also numbers n such that (37*10^n+71)/9 is prime.

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

Links

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

Makoto Kamada, Prime numbers of the form 411...119.

Index entries for primes involving repunits.

Formula

a(n) = A101718(n) + 1.

Mathematica

Do[ If[ PrimeQ[(37*10^n + 71)/9], Print[n]], {n, 0, 10000}]

Prog

(Magma) [n: n in [0..300] | IsPrime((37*10^n+71) div 9)]; // Vincenzo Librandi, Apr 15 2015

Crossrefs

Cf. A002275, A101718.

Sequence in context: A372482 A254405 A216847 * A038583 A082080 A127997

Adjacent sequences: A102980 A102981 A102982 * A102984 A102985 A102986

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 21 2004

Extensions

Addition of a(7)-a(8) from Kamada data by Robert Price, Dec 13 2010

a(9) from Robert Price, Apr 14 2015

Status

approved