The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A104280 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A104280

Numbers n such that 2n+1 is not prime and 2n-1 is prime.
(history; published version)

#18 by Charles R Greathouse IV at Thu Sep 08 08:45:17 EDT 2022

PROG

(MAGMAMagma) [n: n in [0..250]| not IsPrime(2*n+1) and IsPrime(2*n-1)] // Vincenzo Librandi, Jan 28 2011

Discussion

Thu Sep 08

08:45

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

#17 by N. J. A. Sloane at Wed Apr 10 21:50:28 EDT 2019

STATUS

editing

approved

#16 by N. J. A. Sloane at Wed Apr 10 21:50:26 EDT 2019

FORMULA

a(n) = A136798(n)/2. - _Pietro Maiorana_, Jan 12 2019

CROSSREFS

Cf. A136798

Equals A136798/2.

STATUS

approved

editing

#15 by Michel Marcus at Sun Jan 13 02:16:08 EST 2019

STATUS

reviewed

approved

#14 by Joerg Arndt at Sat Jan 12 10:29:00 EST 2019

STATUS

proposed

reviewed

#13 by Joerg Arndt at Sat Jan 12 10:28:57 EST 2019

STATUS

editing

proposed

#12 by Joerg Arndt at Sat Jan 12 10:28:14 EST 2019

FORMULA

a(n) = A136798(n)/2. - _Pietro Maiorana, _, Jan 12 2019

STATUS

proposed

editing

#11 by Pietro Maiorana at Sat Jan 12 08:33:17 EST 2019

STATUS

editing

proposed

Discussion

Sat Jan 12

08:51

Michel Marcus: I would have rather done the reverse : that is a(n) = 2* A104280 (n) in A136798 since A136798 is more recent

09:42

Pietro Maiorana: For a better understanding I wrote also on  A104280. Thank you!

#10 by Pietro Maiorana at Sat Jan 12 08:32:27 EST 2019

FORMULA

a(n) = A136798/2. - Pietro Maiorana, Jan 12 2019

CROSSREFS

Cf. A136798

STATUS

approved

editing

#9 by Charles R Greathouse IV at Tue Jun 13 16:10:32 EDT 2017

STATUS

editing

approved