A102997 Numbers n such that 4*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 463

Offset

1,2

Comments

Also numbers n such that (44*10^n-71)/9 is prime.

No other terms below 10^5.

a(3) > 2*10^5. - Robert Price, Oct 15 2015

a(3) > 8*10^5, if it exists! - Robert Price, Dec 31 2016

Links

Table of n, a(n) for n=1..2.

Makoto Kamada, Prime numbers of the form 488...881.

Index entries for primes involving repunits.

Formula

a(n) = A101734(n) + 1.

Mathematica

Do[ If[ PrimeQ[(44*10^n - 71)/9], Print[n]], {n, 10000}]

Prog

(PARI) for(n=0, 1000, if(isprime((44*10^n-71)/9), print1(n", "))) \\ Altug Alkan, Oct 15 2015

Crossrefs

Cf. A002275, A101734.

Sequence in context: A025038 A028684 A212928 * A252251 A139662 A140030

Adjacent sequences: A102994 A102995 A102996 * A102998 A102999 A103000

Keyword

bref,more,nonn

Author

Robert G. Wilson v, Jan 17 2005

Status

approved