A056694 -id:A056694 - cp's OEIS frontend

A093166 Primes of the form 80*R_k + 3, where R_k is the repunit (A002275) of length k.

3, 83, 883, 88883, 88888883, 888888883, 888888888888883, 888888888888888888888888888888888888888888888888883, 88888888888888888888888888888888888888888888888888888888888888888888883

Offset: 1

Rick L. Shepherd, Mar 26 2004

nonn

Primes of the form (8*10^k - 53)/9. - Vincenzo Librandi, Nov 16 2010

Makoto Kamada, Prime numbers of the form 88...883.
Index entries for primes involving repunits

Cf. A002275, A056694 (corresponding k), A099422.

Select[Table[FromDigits[PadLeft[{3},n,8]],{n,80}],PrimeQ] (* Harvey P. Dale, Sep 21 2013 *)

A099422 Numbers k such that 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Original entry on oeis.org

1, 2, 3, 5, 8, 9, 15, 51, 71, 77, 224, 296, 315, 2090, 2906, 3395, 3882, 5114, 6056, 7254, 7995, 18173, 18971, 35006, 69674, 175428, 253313

Offset: 1

Robert G. Wilson v, Oct 14 2004

nonn

Also numbers k >= 1 such that (8*10^k - 53)/9 is prime.

a(26) > 10^5. - Robert Price, Oct 31 2014

Makoto Kamada, Prime numbers of the form 88...883.
Index entries for primes involving repunits

Cf. A002275, A056664, A056694, A093166.

[n: n in [1..500] | IsPrime((8*10^n-53) div 9)]; // Vincenzo Librandi, Nov 01 2014

Do[ If[ PrimeQ[ 8(10^n - 1)/9 - 5], Print[n]], {n, 1, 5000}]

a(n) = A056694(n) + 1.

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(22)-a(25) from Robert Price, Oct 31 2014
a(1)=0 removed by Georg Fischer, Jan 03 2021
a(26)-a(27) from Kamada data by Tyler Busby, Apr 16 2024

cp's OEIS Frontend

A093166 Primes of the form 80*R_k + 3, where R_k is the repunit (A002275) of length k.

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