The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A056655

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A056655

Numbers k such that 10*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
(history; published version)

#24 by Hugo Pfoertner at Sun Mar 03 04:14:37 EST 2024

STATUS

reviewed

approved

#23 by Michel Marcus at Sun Mar 03 03:20:03 EST 2024

STATUS

proposed

reviewed

#22 by Bill McEachen at Sat Mar 02 21:16:01 EST 2024

STATUS

editing

proposed

#21 by Bill McEachen at Sat Mar 02 21:08:53 EST 2024

DATA

0, 1, 3, 4, 7, 22, 28, 39, 130, 135, 214, 610, 766, 2152, 2575, 22972, 42688, 85711, 85863, 112066, 538507, 631714

COMMENTS

a(23) > 670000 (per the Kamada link). - Bill McEachen, Mar 02 2024

EXTENSIONS

a(20)-a(22) from the Kamada link by Bill McEachen, Mar 02 2024

STATUS

approved

editing

Discussion

Sat Mar 02

21:09

Bill McEachen: (3) new data from the Kamada link

#20 by Susanna Cuyler at Sun Jul 04 22:07:54 EDT 2021

STATUS

proposed

approved

#19 by Jon E. Schoenfield at Sun Jul 04 18:58:50 EDT 2021

STATUS

editing

proposed

#18 by Jon E. Schoenfield at Sun Jul 04 18:58:47 EDT 2021

NAME

Numbers n k such that 10*R_n k + 7 is prime, where R_n k = 11...1 is the repunit (A002275) of length nk.

COMMENTS

Also numbers n k such that (10^(nk+1)+53)/9 is prime.

STATUS

approved

editing

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

LINKS

Makoto Kamada, <a href="httphttps://stdkmd.comnet/nrr/1/11117.htm#prime">Prime numbers of the form 11...117</a>.

Discussion

Thu Jan 17

13:44

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

#16 by Ray Chandler at Sun Apr 26 20:34:47 EDT 2015

STATUS

editing

approved

#15 by Ray Chandler at Sun Apr 26 20:34:43 EDT 2015

LINKS

Makoto Kamada, <a href="http://stdkmd.com/nrr/1/11117.htm#prime">Prime numbers of the form 11...117</a>.

CROSSREFS

Cf. A093139 (corresponding primes), A097684.

Cf. A097684.

STATUS

approved

editing