A103079 Numbers n such that 8*10^n + 4*R_n - 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 26, 36, 38, 60, 80, 92, 174, 486, 627, 999, 1614, 4382, 4898, 8442, 17262, 17802, 35427, 40743

Offset

1,2

Comments

Also numbers n such that (76*10^n-31)/9 is prime.

a(20) > 10^5. - Robert Price, Oct 20 2015

Links

Table of n, a(n) for n=1..19.

Makoto Kamada, Prime numbers of the form 844...441.

Index entries for primes involving repunits.

Formula

a(n) = A101066(n-1) + 1, for n>1.

Mathematica

Do[ If[ PrimeQ[(76*10^n - 31)/9], Print[n]], {n, 0, 10000}]

Prog

(PARI) for(n=0, 1e3, if(isprime((76*10^n-31)/9), print1(n", "))) \\ Altug Alkan, Oct 20 2015

Crossrefs

Cf. A002275, A101066.

Sequence in context: A058763 A291158 A326733 * A046468 A138065 A240897

Adjacent sequences: A103076 A103077 A103078 * A103080 A103081 A103082

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(16)-a(19) from Kamada data by Robert Price, Dec 14 2010

Inserted a(1)=0 by Robert Price, Oct 20 2015

Status

approved