The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A105874 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A105874

Primes for which -2 is a primitive root.
(history; published version)

#37 by Sean A. Irvine at Sun Mar 31 14:59:14 EDT 2024

STATUS

editing

approved

#36 by Sean A. Irvine at Sun Mar 31 14:57:50 EDT 2024

LINKS

<a href="/index/Pri#primes_root">Index entries for primes by primitive root</a>

STATUS

approved

editing

#35 by N. J. A. Sloane at Sat Aug 12 00:29:13 EDT 2023

STATUS

proposed

approved

#34 by Michel Marcus at Fri Aug 11 11:45:04 EDT 2023

STATUS

editing

proposed

#33 by Michel Marcus at Fri Aug 11 11:45:00 EDT 2023

PROG

from itertools import islice

STATUS

proposed

editing

#32 by Chai Wah Wu at Fri Aug 11 11:01:49 EDT 2023

STATUS

editing

proposed

#31 by Chai Wah Wu at Fri Aug 11 11:01:47 EDT 2023

PROG

(Python)

from sympy import n_order, nextprime

def A105874_gen(startvalue=3): # generator of terms >= startvalue

p = max(startvalue-1, 2)

while (p:=nextprime(p)):

if n_order(-2, p) == p-1:

yield p

A105874_list = list(islice(A105874_gen(), 20)) # Chai Wah Wu, Aug 11 2023

STATUS

approved

editing

#30 by N. J. A. Sloane at Thu Jun 04 20:20:34 EDT 2015

STATUS

editing

approved

#29 by N. J. A. Sloane at Thu Jun 04 20:20:29 EDT 2015

FORMULA

Let a(p,q)=sum(n=1,2*p*q,2*cos(2^n*Pi/((2*q+1)*(2*p+1)))). Then 2*p+1 is a prime of belonging to this sequence when a(p,1)==1. - Gerry Martens, May 21 2015

STATUS

proposed

editing

#28 by Michel Marcus at Wed Jun 03 02:20:35 EDT 2015

STATUS

editing

proposed

Discussion

Wed Jun 03

16:06

Gerry Martens: I like Robert's idea but have not been able to find an asymptotic formula for larger or big n values.