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 A352786 #67 Jun 09 2022 08:45:37
%S A352786 1,-1,-3,-6,-18,-27,-108,-81,-486,0,-1458,8748,-6561,118098,118098,
%T A352786 1003833,1417176,11691702,9565938,105225318,114791256,746143164,
%U A352786 1076168025,7231849128,2324522934,58113073350,45328197213,334731302496,146444944842,3263630199336,-3012581722464
%N A352786 Expansion of Product_{k>=1} (1 - 3^(k-1)*x^k).
%F A352786 a(n) = Sum_{k=0..A003056(n)} (-1)^k * q(n,k) * 3^(n-k), where q(n,k) is the number of partitions of n into k distinct parts.
%t A352786 nmax = 30; CoefficientList[Series[Product[(1 - 3^(k - 1) x^k), {k, 1, nmax}], {x, 0, nmax}], x]
%t A352786 Table[Sum[(-1)^k Length[Select[IntegerPartitions[n, {k}], UnsameQ @@ # &]] 3^(n - k), {k, 0, Floor[(Sqrt[8 n + 1] - 1)/2]}], {n, 0, 30}]
%Y A352786 Cf. A003056, A032308, A242587, A261582, A292128, A300579, A337299, A344062, A352762.
%K A352786 sign
%O A352786 0,3
%A A352786 _Ilya Gutkovskiy_, Jun 08 2022