The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A102931 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A102931

Numbers k such that 10^k + 2*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
(history; published version)

#28 by Charles R Greathouse IV at Wed Feb 01 23:06:59 EST 2023

STATUS

proposed

approved

#27 by Tyler Busby at Wed Feb 01 22:28:59 EST 2023

STATUS

editing

proposed

#26 by Tyler Busby at Wed Feb 01 22:28:56 EST 2023

COMMENTS

a(15) > 2*10^5. - Tyler Busby, Feb 01 2023

STATUS

approved

editing

#25 by Alois P. Heinz at Tue Jan 31 15:02:18 EST 2023

STATUS

reviewed

approved

#24 by Michel Marcus at Tue Jan 31 14:58:10 EST 2023

STATUS

proposed

reviewed

#23 by Tyler Busby at Tue Jan 31 14:06:24 EST 2023

STATUS

editing

proposed

#22 by Tyler Busby at Tue Jan 31 14:06:16 EST 2023

DATA

1, 3, 6, 51, 57, 63, 150, 393, 420, 547, 42024, 43063, 101613, 107385

EXTENSIONS

a(13)-a(14) from Tyler Busby, Jan 31 2023

STATUS

approved

editing

#21 by Joerg Arndt at Thu Jul 08 03:11:26 EDT 2021

STATUS

proposed

approved

#20 by Jon E. Schoenfield at Thu Jul 08 01:44:38 EDT 2021

STATUS

editing

proposed

#19 by Jon E. Schoenfield at Thu Jul 08 01:44:36 EDT 2021

NAME

Numbers n k such that 10^n k + 2*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 (11*10^nk + 61)/9 is prime.

STATUS

approved

editing