The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A004022

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A004022

Primes of the form (10^k - 1)/9. Also called repunit primes or repdigit primes.
(history; published version)

#94 by N. J. A. Sloane at Tue Nov 05 12:12:55 EST 2024

STATUS

proposed

approved

#93 by Michael De Vlieger at Tue Nov 05 09:27:19 EST 2024

STATUS

editing

proposed

#92 by Michael De Vlieger at Tue Nov 05 09:27:18 EST 2024

LINKS

Dmytro S. Inosov and Emil Vlasák, <a href="https://arxiv.org/abs/2410.21427">Cryptarithmically unique terms in integer sequences</a>, arXiv:2410.21427 [math.NT], 2024. See p. 18.

STATUS

approved

editing

#91 by N. J. A. Sloane at Sun Jan 22 07:15:58 EST 2023

STATUS

editing

approved

#90 by N. J. A. Sloane at Sun Jan 22 07:15:53 EST 2023

NAME

Primes of the form (10^k - 1)/9. Also called repunit primes or repdigit primes.

CROSSREFS

A116692 is another version of repunit primes or repdigit primes. - N. J. A. Sloane, Jan 22 2023

EXTENSIONS

Name expanded by N. J. A. Sloane, Jan 22 2023

STATUS

approved

editing

#89 by Charles R Greathouse IV at Thu Sep 08 08:44:32 EDT 2022

PROG

(MAGMAMagma) [a: n in [0..300] | IsPrime(a) where a is (10^n - 1) div 9 ]; // Vincenzo Librandi, Nov 08 2014

Discussion

Thu Sep 08

08:44

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

#88 by Alois P. Heinz at Thu Jun 09 21:12:27 EDT 2022

STATUS

proposed

approved

#87 by Michael S. Branicky at Thu Jun 09 20:28:53 EDT 2022

STATUS

editing

proposed

#86 by Michael S. Branicky at Thu Jun 09 20:28:51 EDT 2022

PROG

(Python)

from sympy import isprime

from itertools import count, islice

def agen(): # generator of terms

yield from (t for t in (int("1"*k) for k in count(1)) if isprime(t))

print(list(islice(agen(), 4))) # Michael S. Branicky, Jun 09 2022

STATUS

approved

editing

#85 by Michael De Vlieger at Fri Apr 01 20:20:00 EDT 2022

STATUS

editing

approved