login
A286187
Number of connected induced (non-null) subgraphs of the web graph with 3n nodes.
16
6, 33, 188, 985, 4990, 24645, 119712, 574225, 2727218, 12847821, 60115060, 279652793, 1294441894, 5965567125, 27387631368, 125308264225, 571591760602, 2600204421405, 11799376912220, 53424388364873, 241398575303374, 1088727972172389, 4901842528232304, 22034981672761649
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Vertex-Induced Subgraph
Eric Weisstein's World of Mathematics, Web Graph
FORMULA
Empirical g.f.: x*(6 - 39*x + 92*x^2 - 101*x^3 + 32*x^4 - 8*x^5 + 64*x^6 - 48*x^7) / ((1 - x)^2*(1 - 5*x + 2*x^2 + 4*x^3)^2). - Colin Barker, May 21 2017
MATHEMATICA
{6, 33} ~Join~ Table[g = GraphData[{"Web", n}]; -1 + ParallelSum[Boole@ ConnectedGraphQ@ Subgraph[g, s], {s, Subsets@ Range[3 n]}], {n, 3, 6}]
CROSSREFS
Cf. A020873 (wheel), A059020 (ladder), A059525 (grid), A286139 (king), A286182 (prism), A286183 (antiprism), A286184 (helm), A286185 (Möbius ladder), A286186 (friendship), A286188 (gear), A286189 (rook), A285765 (queen).
Sequence in context: A180035 A360717 A379139 * A260774 A218182 A093964
KEYWORD
nonn
AUTHOR
Giovanni Resta, May 04 2017
EXTENSIONS
a(12)-a(24) from Andrew Howroyd, May 20 2017
STATUS
approved