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.

A061072 Smallest integer with A002191(n) divisors, i.e., the number of divisors equals the sum of the divisors of a different number.

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%I A061072 #15 Mar 15 2025 11:29:54
%S A061072 1,4,6,12,64,24,60,4096,192,144,180,240,360,960,720,1073741824,840,
%T A061072 1260,786432,36864,1680,2880,15360,2520,6300,6720,2359296,5040,
%U A061072 3221225472,14400,983040,10080,206158430208,184320,15120,20160,25200,2985984,9663676416,27720
%N A061072 Smallest integer with A002191(n) divisors, i.e., the number of divisors equals the sum of the divisors of a different number.
%H A061072 Amiram Eldar, <a href="/A061072/b061072.txt">Table of n, a(n) for n = 1..959</a>
%F A061072 A000005(a(n)) = A002191(n). I.e., if function A000005 is applied to this sequence, then values of A002191 are obtained. These terms are taken from A005179.
%F A061072 a(n) = A005179(A002191(n)). - _David Wasserman_, Jun 06 2002
%e A061072 For all values of sigma(x), i.e., of A002191, the smallest number with identical number of divisors is found at A005179(sigma(x)). E.g., 8 = A002191(6) is a possible divisor sum. The smallest number which has 8 divisors is 24 = A005179(8). See also comment to A008864, with special solutions of equation: sigma(x) = tau(y) = A000203(x) = A000005(y).
%Y A061072 Cf. A000005, A000203, A002191, A005179, A008864.
%K A061072 nonn
%O A061072 1,2
%A A061072 _Labos Elemer_, May 28 2001
%E A061072 More terms from _David Wasserman_, Jun 06 2002
%E A061072 Offset corrected by _Sean A. Irvine_, Jan 19 2023