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 A286139 #17 Feb 16 2025 08:33:44
%S A286139 1,15,388,37196,14765089,24076152503,159850328891568,
%T A286139 4290837646252661680,463376724731585422732393,
%U A286139 200665409586497566263900755703,347694350828123116321061347501951972,2406781070555276417850396576804205226358828,66481859567653621586313146932097075651519991887257
%N A286139 Number of connected induced (non-null) subgraphs of the n X n king graph.
%H A286139 Andrew Howroyd, <a href="/A286139/b286139.txt">Table of n, a(n) for n = 1..16</a>
%H A286139 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/KingGraph.html">King Graph</a>
%H A286139 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Vertex-InducedSubgraph.html">Vertex-Induced Subgraph</a>
%t A286139 Table[If[n<2, n, g = GraphData[{"King", {n, n}}]; -1 + ParallelSum[ Boole@ ConnectedGraphQ@ Subgraph[g, s], {s, Subsets@ Range[n^2]}]], {n, 4}]
%Y A286139 Cf. A020873 (wheel), A059020 (ladder), A059525 (grid), A286182 (prism), A286183 (antiprism), A286184 (helm), A286185 (Möbius ladder), A286186 (friendship), A286187 (web), A286188 (gear), A286189 (rook), A285765 (queen).
%K A286139 nonn,hard
%O A286139 1,2
%A A286139 _Giovanni Resta_, May 03 2017
%E A286139 a(10)-a(13) from _Andrew Howroyd_, May 20 2017