cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A139719 A number m is included if k + m/k divides m for at least one divisor k of m.

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%I A139719 #15 Jul 20 2019 18:29:08
%S A139719 4,16,18,36,48,64,72,100,144,150,162,180,192,196,256,288,294,324,400,
%T A139719 432,448,450,484,490,576,588,600,648,676,720,768,784,882,900,960,1024,
%U A139719 1134,1152,1156,1176,1200,1210,1296,1350,1444,1458,1584,1600,1620,1728
%N A139719 A number m is included if k + m/k divides m for at least one divisor k of m.
%C A139719 All terms are even. All even perfect squares are included. If m is included, then 4m is also included.
%C A139719 Also the set of all numbers m of the form m = r*s*(r+s)^2*t^2 with positive integers r,s,t; if one additionally requires (r,s) = 1 and r <= s, then there is exactly one such representation for each m. [From _Hagen von Eitzen_, Jul 22 2009]
%H A139719 Amiram Eldar, <a href="/A139719/b139719.txt">Table of n, a(n) for n = 1..10000</a>
%e A139719 72 is included because 6 is a divisor of 72 and (6 + 72/6) = 18 divides 72.
%t A139719 nkdQ[n_]:=Module[{divs=Most[Divisors[n]]},MemberQ[Divisible[n,#]&/@ (#+n/#&/@ divs),True]]; Select[Range[2000],nkdQ] (* _Harvey P. Dale_, Apr 24 2012 *)
%Y A139719 Cf. A139718.
%K A139719 nonn
%O A139719 1,1
%A A139719 _Leroy Quet_, May 01 2008
%E A139719 Extended by _Ray Chandler_, Jul 01 2009