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 A287426 #12 Feb 16 2025 08:33:46
%S A287426 3,14,47,164,577,2046,7275,25896,92213,328402,1169599,4165564,
%T A287426 14835849,52838630,188187539,670239824,2387094493,8501763066,
%U A287426 30279478119,107841960420,384084837425,1367938433038,4871984973883,17351831787640,61799465310597,220102059506978
%N A287426 Number of connected induced subgraphs in the n-sun graph.
%H A287426 Colin Barker, <a href="/A287426/b287426.txt">Table of n, a(n) for n = 1..1000</a>
%H A287426 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SunGraph.html">Sun Graph</a>
%H A287426 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Vertex-InducedSubgraph.html">Vertex-Induced Subgraph</a>
%H A287426 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (5,-5,-1,2).
%F A287426 a(n) = A206776(n) + n - 1.
%F A287426 From _Colin Barker_, May 25 2017: (Start)
%F A287426 G.f.: x*(3 - x - 8*x^2 + 2*x^3)/((1 - x)^2*(1 - 3*x - 2*x^2)).
%F A287426 a(n) = -1 + n + ((3-sqrt(17))/2)^n + ((3+sqrt(17))/2)^n.
%F A287426 a(n) = 5*a(n-1) - 5*a(n-2) - a(n-3) + 2*a(n-4) for n>4. (End)
%t A287426 LinearRecurrence[{5, -5, -1, 2}, {3, 14, 47, 164}, 20]
%o A287426 (PARI) Vec(x*(3 - x - 8*x^2 + 2*x^3) / ((1 - x)^2*(1 - 3*x - 2*x^2)) + O(x^40)) \\ _Colin Barker_, May 25 2017
%Y A287426 Cf. A206776.
%K A287426 nonn,easy
%O A287426 1,1
%A A287426 _Eric W. Weisstein_, May 24 2017