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 A363644 #13 Jul 19 2023 02:19:21
%S A363644 0,0,1,3,6,11,15,27,29,60,45,145,66,318,146,789,120,2199,153,4890,
%T A363644 1406,11730,231,34175,426,67884,20738,163956,378,453341,435,882153,
%U A363644 295742,1966608,10230,5656484,630,10027674,3897938,23069916,780,63648517,861,113050536
%N A363644 Expansion of Sum_{k>0} x^(3*k)/(1 - k*x^k)^3.
%F A363644 a(n) = Sum_{d|n} (n/d)^(d-3) * binomial(d-1,2).
%t A363644 a[n_] := DivisorSum[n, (n/#)^(# - 3)*Binomial[# - 1, 2] &]; Array[a, 50] (* _Amiram Eldar_, Jul 18 2023 *)
%o A363644 (PARI) a(n) = sumdiv(n, d, (n/d)^(d-3)*binomial(d-1, 2));
%Y A363644 Cf. A363639, A363642, A363643.
%Y A363644 Cf. A363610, A363652.
%K A363644 nonn
%O A363644 1,4
%A A363644 _Seiichi Manyama_, Jun 13 2023