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 A328890 #11 Feb 16 2025 08:33:58
%S A328890 1,6,18,46,110,254,574,1278,2814,6142,13310,28670,61438,131070,278526,
%T A328890 589822,1245182,2621438,5505022,11534334,24117246,50331646,104857598,
%U A328890 218103806,452984830,939524094,1946157054,4026531838,8321499134,17179869182,35433480190,73014444030
%N A328890 Number of acyclic edge covers of the complete bipartite graph K_{n,2}.
%H A328890 Andrew Howroyd, <a href="/A328890/b328890.txt">Table of n, a(n) for n = 1..1000</a>
%H A328890 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CompleteBipartiteGraph.html">Complete Bipartite Graph</a>
%H A328890 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5,-8,4).
%F A328890 a(n) = 2*A000225(n-1) + A001787(n).
%F A328890 a(n) = (2 + n)*2^(n-1) - 2.
%F A328890 From _Colin Barker_, Nov 05 2019: (Start)
%F A328890 G.f.: x*(1 + x - 4*x^2) / ((1 - x)*(1 - 2*x)^2).
%F A328890 a(n) = 5*a(n-1) - 8*a(n-2) + 4*a(n-3) for n>3.
%F A328890 (End)
%o A328890 (PARI) a(n) = {(2 + n)*2^(n-1) - 2}
%o A328890 (PARI) Vec(x*(1 + x - 4*x^2) / ((1 - x)*(1 - 2*x)^2) + O(x^30)) \\ _Colin Barker_, Nov 05 2019
%Y A328890 Column 2 of A328888.
%Y A328890 Cf. A000225, A001787.
%K A328890 nonn,easy
%O A328890 1,2
%A A328890 _Andrew Howroyd_, Oct 29 2019