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 A384086 #12 May 19 2025 10:02:45
%S A384086 1,4,72,2352,112000,7023540,546991704,50923706176,5517464159232,
%T A384086 682067031126660,94744306830613000,14610279918692775504,
%U A384086 2476682373835289303424,457771369968515293229812,91624876032673265663215800,19743379886572250897986694400,4556982707091255612929249419264
%N A384086 a(n) = [x^n] Product_{k=1..n} ((1 + k*x)/(1 - k*x))^2.
%F A384086 a(n) ~ c * d^n * n! / n, where d = 15.357995623209995052090556511543938190953157405669200... and c = 0.3746298100044008083790505105262276548713201624206421...
%t A384086 Table[SeriesCoefficient[Product[(1+k*x)^2/(1-k*x)^2, {k, 1, n}], {x, 0, n}], {n, 0, 20}]
%Y A384086 Cf. A129256, A350376.
%Y A384086 Cf. A350366, A384087, A384088, A351764.
%K A384086 nonn
%O A384086 0,2
%A A384086 _Vaclav Kotesovec_, May 19 2025