The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A160921

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A160921

Numbers k such that k / (A000005(k)*(A000005(k)+1)/2) is an integer.
(history; published version)

#18 by Harvey P. Dale at Sun Aug 20 11:44:36 EDT 2023

STATUS

editing

approved

#17 by Harvey P. Dale at Sun Aug 20 11:44:33 EDT 2023

MATHEMATICA

dsiQ[n_]:=With[{d=DivisorSigma[0, n]}, IntegerQ[n/((d(d+1))/2)]]; Select[Range[10000], dsiQ] (* Harvey P. Dale, Aug 20 2023 *)

STATUS

approved

editing

#16 by OEIS Server at Sun Jan 17 02:58:21 EST 2021

LINKS

Amiram Eldar, <a href="/A160921/b160921_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..136 from R. J. Mathar)

#15 by Vaclav Kotesovec at Sun Jan 17 02:58:21 EST 2021

STATUS

reviewed

approved

Discussion

Sun Jan 17

02:58

OEIS Server: Installed new b-file as b160921.txt.  Old b-file is now b160921_1.txt.

#14 by Michel Marcus at Sun Jan 17 02:31:22 EST 2021

STATUS

proposed

reviewed

#13 by Amiram Eldar at Sun Jan 17 02:13:47 EST 2021

STATUS

editing

proposed

#12 by Amiram Eldar at Sun Jan 17 02:04:18 EST 2021

MATHEMATICA

t[n_] := n*(n + 1)/2; Select[Range[10^4], Divisible[#, t[DivisorSigma[0, #]]] &] (* Amiram Eldar, Jan 17 2021 *)

#11 by Amiram Eldar at Sun Jan 17 02:02:54 EST 2021

NAME

Numbers n k such that n k / (A000005(nk)*(A000005(nk)+1)/2) is an integer.

CROSSREFS

Cf. A000005, A033950.

#10 by Amiram Eldar at Sun Jan 17 02:02:34 EST 2021

LINKS

Amiram Eldar, <a href="/A160921/b160921_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..136 from R. J. Mathar)

#9 by Amiram Eldar at Sun Jan 17 02:02:21 EST 2021

LINKS

R. J. Mathar, Amiram Eldar, <a href="/A160921/b160921_1.txt">Table of n, a(n) for n = 1..13610000</a>

STATUS

approved

editing