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 A239668 #35 Jul 06 2017 17:41:36
%S A239668 0,4,9,28,25,85,49,124,117,209,121,397,169,389,394,508,289,841,361,
%T A239668 953,730,917,529,1645,775,1265,1089,1757,841,2810,961,2044,1714,2129,
%U A239668 1754,3745,1369,2645,2362,3929,1681,5174,1849,4109,3742,3845,2209,6637,2793,5459,3970
%N A239668 Sum of the composite divisors of n^2.
%H A239668 Harvey P. Dale, <a href="/A239668/b239668.txt">Table of n, a(n) for n = 1..1000</a>
%F A239668 a(n) = sigma(n^2) - sopf(n^2) - 1.
%F A239668 a(n) = A000203(n^2) - A008472(n^2) - 1. - _Wesley Ivan Hurt_, Mar 30 2014
%F A239668 a(n) = A023891(n^2). - _Michel Marcus_, Mar 31 2014
%F A239668 a(n) = n^2 if n is prime. - _Zak Seidov_, Mar 31 2014
%e A239668 For n=2, the sum of the composite factors of n^2 is equal to 4.
%p A239668 A008472 := n -> add(d, d = select(isprime, numtheory[divisors](n))):
%p A239668 f:=n->numtheory[sigma](n^2)-A008472(n)-1; [seq(f(n),n=1..100)]; # _N. J. A. Sloane_, Mar 31 2014
%t A239668 a[n_] := DivisorSum[n^2, If[# == 1 || PrimeQ[#], 0, #]& ]; Array[a, 60] (* _Jean-François Alcover_, Dec 18 2015 *)
%t A239668 Table[Total[Select[Divisors[n^2],CompositeQ]],{n,60}] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 06 2017 *)
%o A239668 (PARI) a(n) = sumdiv(n^2, d, d*(!isprime(d) && (d != 1))); \\ _Michel Marcus_, Mar 31 2014
%Y A239668 Cf. A000040, A000720, A023891.
%K A239668 nonn
%O A239668 1,2
%A A239668 _Janet Lee_, Mar 23 2014
%E A239668 Formula corrected by _Wesley Ivan Hurt_, Mar 30 2014
%E A239668 More terms from _N. J. A. Sloane_, Mar 31 2014