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.
%I A063975 #13 Aug 12 2017 00:18:29
%S A063975 1,12,24,60,120,72,216,288,1320,480,240,840,1296,2700,960,1512,1080,
%T A063975 720,1728,2016,3840,3240,3456,2520,3360,3024,1440,3600,6912,2160,
%U A063975 19152,2880,7920,13680,9072,12600,6048,5040,18000,6480,27216,13440,7200,27648,5760
%N A063975 Smallest numbers such that the number of terms in inverse set usigma equals n; where usigma = A034448.
%H A063975 Donovan Johnson, <a href="/A063975/b063975.txt">Table of n, a(n) for n = 1..3000</a>
%e A063975 usigma(x) = 288, invusigma(288) = {138, 154, 165, 168, 213, 235, 248, 253}, so a(288) = 8, the number of all terms in the inverse set and all similar numbers are larger: {288, 648, 672, 900}.
%p A063975 with(numtheory): A034448 := proc(n) option remember: local ans,i: ans:=1: for i from 1 to nops(ifactors(n)[2]) do ans := ans*(1+ifactors(n)[ 2 ][ i ][ 1 ]^ifactors(n)[ 2 ] [ i ] [ 2 ]): od: return ans: end: for n from 1 to 5000 do m:=A034448(n): if(type(ct[m],integer))then ct[m]:=ct[m]+1: else ct[m]:=1: fi:od: for m from 1 to 28 do for n from 1 to 5000 do if(ct[n]=m)then printf("%d, ",n):break: fi: od:od: # _Nathaniel Johnston_, Apr 29 2011
%Y A063975 Cf. A034444, A034448, A051444, A054973, A057637.
%K A063975 nonn
%O A063975 1,2
%A A063975 _Labos Elemer_, Sep 05 2001
%E A063975 a(9) - a(45) from _Nathaniel Johnston_, Apr 29 2011