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.

A335544 Numbers with more abundant divisors than deficient divisors.

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%I A335544 #12 Jun 14 2020 01:24:51
%S A335544 216,240,288,360,432,480,504,540,576,600,648,672,720,792,840,864,936,
%T A335544 960,972,1008,1056,1080,1120,1152,1200,1248,1260,1296,1320,1344,1440,
%U A335544 1512,1560,1584,1620,1680,1728,1800,1872,1920,1944,2016,2112,2160,2240,2268,2304
%N A335544 Numbers with more abundant divisors than deficient divisors.
%C A335544 This sequence is infinite. For example, 216*p is a term for all primes p.
%C A335544 The least odd term of this sequence is a(16317321) = 638512875.
%C A335544 Apparently, this sequence has an asymptotic density of about 0.025.
%H A335544 Amiram Eldar, <a href="/A335544/b335544.txt">Table of n, a(n) for n = 1..10000</a>
%F A335544 Numbers k such that A080224(k) > A080226(k).
%e A335544 216 is a term since it has 8 abundant divisors, {12, 18, 24, 36, 54, 72, 108, 216}, and only 7 deficient divisors, {1, 2, 3, 4, 8, 9, 27}.
%t A335544 ab[n_] := DivisorSigma[1, n] - 2n; moreAbQ[n_] := Count[(abs = ab/@Divisors[n]), _?(# > 0 &)] > Count[abs, _?(# < 0 &)]; Select[Range[50000], moreAbQ]
%Y A335544 Cf. A000203, A005100, A005101, A080224, A080226, A335543.
%K A335544 nonn
%O A335544 1,1
%A A335544 _Amiram Eldar_, Jun 13 2020