The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A217791 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A217791

Numbers k such that sigma(k) = 3*sigma(k+1).
(history; published version)

#30 by Wesley Ivan Hurt at Tue Jan 24 15:30:34 EST 2023

STATUS

editing

approved

#29 by Wesley Ivan Hurt at Tue Jan 24 15:30:13 EST 2023

NAME

Numbers n k such that sigma(nk) = 3*sigma(nk+1).

STATUS

approved

editing

#28 by Charles R Greathouse IV at Thu Sep 08 08:46:04 EDT 2022

PROG

(MAGMAMagma) [n: n in [1..10^7] | SumOfDivisors(n) eq 3*SumOfDivisors(n+1)]; // Bruno Berselli, Mar 25 2013

Discussion

Thu Sep 08

08:46

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

#27 by Peter Luschny at Tue Jul 16 17:41:59 EDT 2019

STATUS

proposed

approved

#26 by Omar E. Pol at Tue Jul 16 13:35:30 EDT 2019

STATUS

editing

proposed

#25 by Omar E. Pol at Tue Jul 16 13:34:58 EDT 2019

CROSSREFS

Cf. A000203, A002961, A058073, A067081, A077087, A163193, A272027 (3*sigma(n)).

STATUS

approved

editing

Discussion

Tue Jul 16

13:35

Omar E. Pol: Added a cross-reference.

#24 by Harvey P. Dale at Mon Oct 17 16:36:34 EDT 2016

STATUS

editing

approved

#23 by Harvey P. Dale at Mon Oct 17 16:36:28 EDT 2016

MATHEMATICA

Position[Partition[DivisorSigma[1, Range[78*10^5]], 2, 1], _?(#[[1]] == 3#[[2]]&), {1}, Heads->False]//Flatten (* Harvey P. Dale, Oct 17 2016 *)

STATUS

approved

editing

#22 by Joerg Arndt at Sat Apr 06 04:58:01 EDT 2013

STATUS

reviewed

approved

#21 by Giovanni Resta at Sat Apr 06 03:46:38 EDT 2013

STATUS

proposed

reviewed