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 A363975 #10 Jun 30 2023 15:36:04
%S A363975 1,1,1,4,1,1,7,4,1,11,1,4,16,7,1,25,1,1,29,14,7,37,1,4,46,16,1,65,1,
%T A363975 11,67,25,1,79,7,4,92,29,16,119,1,7,121,40,1,137,1,25,160,56,1,190,1,
%U A363975 1,191,65,29,211,1,14,232,67,7,278,16,37,277,82,1,317,1,4,326,92,46,383,7,16,379
%N A363975 Expansion of Sum_{k>0} x^k / (1 - x^(3*k))^3.
%F A363975 G.f.: Sum_{k>0} k*(k+1)/2 * x^(3*k-2) / (1 - x^(3*k-2)).
%F A363975 a(n) = Sum_{d|n, d==1 mod 3} binomial((d+2)/3+1,2).
%t A363975 a[n_] := DivisorSum[n, Binomial[(#+2)/3+1,2] &, Mod[#, 3] == 1 &]; Array[a, 100] (* _Amiram Eldar_, Jun 30 2023 *)
%o A363975 (PARI) a(n) = sumdiv(n, d, (d%3==1)*binomial((d+2)/3+1, 2));
%Y A363975 Cf. A001817, A363901.
%Y A363975 Cf. A363970.
%K A363975 nonn
%O A363975 1,4
%A A363975 _Seiichi Manyama_, Jun 30 2023