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 A361471 #20 May 18 2023 01:56:21
%S A361471 4,4,4,4,8,12,16,16,16,16,20,20,24,24,24,24,28,32,36,36,36,36,40,40,
%T A361471 44,44,44,44,48,52,56,56,56,56,60,60,64,64,64,64,68,72,76,76,76,76,80,
%U A361471 80,84,84,84,84,88,92,96,96,96,96,100,100,104,104,104,104,108
%N A361471 Size of the symmetric difference of {1,2,3,4}, {2,4,6,8}, ..., {n,2n,3n,4n}.
%H A361471 P. Y. Huang, W. F. Ke, and G. F. Pilz, <a href="https://doi.org/10.1090/S0002-9939-09-10189-2">The cardinality of some symmetric differences</a>, Proc. Amer. Math. Soc., 138 (2010), 787-797.
%H A361471 <a href="/index/Rec#order_13">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,0,0,0,0,0,0,1,-1).
%F A361471 G.f.: 4*x*(x^10+x^6+x^5+x^4+1)/(x^13-x^12-x+1). - _Alois P. Heinz_, May 17 2023
%t A361471 delta[l_, m_] := Complement[Join[l, m], Intersection[l, m]];
%t A361471 Nabl[s_, n_] := (d = {}; Do[d = delta[d, s*j], {j, Range[n]}]; d);
%t A361471 Table[Length[Nabl[Range[1, 4], n]], {n, 100}]
%Y A361471 Cf. A361458.
%K A361471 nonn,easy
%O A361471 1,1
%A A361471 _Guenter Pilz_, May 17 2023