A103082 Numbers n such that 8*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 4, 13, 37, 46, 106, 139, 469, 5695, 56281, 58669

Offset

1,3

Comments

Also numbers n such that (76*10^n+41)/9 is prime.

a(13) > 10^5. - Robert Price, Oct 18 2015

Links

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

Makoto Kamada, Prime numbers of the form 844...449.

Index entries for primes involving repunits.

Formula

a(n) = A101069(n-1) + 1 for n>1.

Mathematica

Do[ If[ PrimeQ[(76*10^n + 41)/9], Print[n]], {n, 0, 10000}]

Prog

(PARI) for(n=0, 1e5, if(isprime(k=(76*10^n+41)/9), print1(n", "))) \\ Altug Alkan, Oct 19 2015

Crossrefs

Cf. A002275, A101069.

Sequence in context: A222425 A222189 A003727 * A279111 A299111 A324250

Adjacent sequences: A103079 A103080 A103081 * A103083 A103084 A103085

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

Inserted a(1)=0 and added a(11)-a(12) by Robert Price, Oct 18 2015

Status

approved