The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A056693

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A056693

Numbers k such that 70*R_k + 9 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
(history; published version)

#31 by Alois P. Heinz at Wed Feb 01 18:07:06 EST 2023

STATUS

proposed

approved

#30 by Tyler Busby at Wed Feb 01 18:05:30 EST 2023

STATUS

editing

proposed

#29 by Tyler Busby at Wed Feb 01 18:05:18 EST 2023

DATA

1, 65, 85, 89, 101, 385, 623, 7783, 18535, 113756, 135878

COMMENTS

a(12) > 2*10^5. - Tyler Busby, Feb 01 2023

EXTENSIONS

a(10)-a(11) from Tyler Busby, Feb 01 2023

STATUS

approved

editing

#28 by Charles R Greathouse IV at Thu Sep 08 08:45:01 EDT 2022

PROG

(MAGMAMagma) [n: n in [1..400] | IsPrime((7*10^(n+1)+11) div 9)]; Vincenzo Librandi, Nov 22 2014

Discussion

Thu Sep 08

08:45

OEIS Server: https://oeis.org/edit/global/2944

#27 by Susanna Cuyler at Sun Jul 04 22:10:17 EDT 2021

STATUS

proposed

approved

#26 by Jon E. Schoenfield at Sun Jul 04 19:08:50 EDT 2021

STATUS

editing

proposed

#25 by Jon E. Schoenfield at Sun Jul 04 19:08:49 EDT 2021

NAME

Numbers n k such that 70*R_n k + 9 is prime, where R_n k = 11...1 is the repunit (A002275) of length nk.

COMMENTS

Also numbers n k such that (7*10^(nk+1)+11)/9 is prime.

STATUS

approved

editing

#24 by Charles R Greathouse IV at Thu Jan 17 13:44:05 EST 2019

LINKS

Makoto Kamada, <a href="httphttps://stdkmd.comnet/nrr/7/77779.htm#prime">Prime numbers of the form 77...779</a>.

Discussion

Thu Jan 17

13:44

OEIS Server: https://oeis.org/edit/global/2791

#23 by Ray Chandler at Thu May 21 19:16:45 EDT 2015

STATUS

editing

approved

#22 by Ray Chandler at Thu May 21 19:16:42 EDT 2015

CROSSREFS

Cf. A002275, A093404, A098089.

STATUS

approved

editing