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A290757 Number of (non-null) connected induced subgraphs in the (2 n)-crossed prism graph. 2
167, 1666, 14861, 125972, 1034803, 8313830, 65687321, 512243704, 3952731839, 30238302794, 229652377381, 1733456444636, 13015423731275, 97276566448558, 724116167445041, 5371074588248768, 39713352030673111, 292804273605231122, 2153305580970250301 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Andrew Howroyd, Table of n, a(n) for n = 2..200

Eric Weisstein's World of Mathematics, Connected Graph

Eric Weisstein's World of Mathematics, Crossed Prism Graph

Eric Weisstein's World of Mathematics, Vertex-Induced Subgraph

Index entries for linear recurrences with constant coefficients, signature (16, -78, 112, -49).

FORMULA

From Andrew Howroyd, Aug 31 2017: (Start)

a(n) = 7^n + n*(191*7^(n-2) - 14)/3.

a(n) = 16*a(n-1) - 78*a(n-2) + 112*a(n-3) - 49*a(n-4) for n > 5.

G.f.: x^2*(167 - 1006*x + 1231*x^2 - 560*x^3)/((1 - x)^2 * (1 - 7*x)^2).

(End)

MATHEMATICA

DeleteCases[#, 0] &@ CoefficientList[Series[x^2*(167 - 1006 x + 1231 x^2 - 560 x^3)/((1 - x)^2*(1 - 7 x)^2), {x, 0, 20}], x] (* Michael De Vlieger, Aug 31 2017 *)

a[n_] := (1/21)*(191*7^(n-1)*(n-1) - 98*(n-1) + 338*7^(n-1) - 98);

Table[a[n], {n, 2, 30}] (* Jean-Fran├žois Alcover, Nov 08 2017, after Andrew Howroyd *)

LinearRecurrence[{16, -78, 112, -49}, {167, 1666, 14861, 125972}, 20] (* Eric W. Weisstein, Jan 13 2018 *)

PROG

(PARI) Vec((167 - 1006*x + 1231*x^2 - 560*x^3)/((1 - x)^2 * (1 - 7*x)^2) + O(x^30)) \\ Andrew Howroyd, Aug 31 2017

CROSSREFS

Cf. A287430.

Sequence in context: A250586 A201853 A142843 * A012021 A175558 A289743

Adjacent sequences:  A290754 A290755 A290756 * A290758 A290759 A290760

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Aug 09 2017

EXTENSIONS

Terms a(8) and beyond from Andrew Howroyd, Aug 31 2017

STATUS

approved

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Last modified August 4 09:03 EDT 2020. Contains 336201 sequences. (Running on oeis4.)