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A020879 Number of elementary edge-subgraphs in Moebius ladder M_n. 1
17, 58, 181, 602, 2006, 6797, 23205, 79771, 275462, 954367, 3314074, 11526782, 40136519, 139865123, 487656165, 1700907382, 5934174209, 20707036102, 72265263946, 252219473921, 880346196329, 3072884622527, 10726335768378, 37442520667627, 130702738526702 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..26.

Sean A. Irvine, Java program (github).

J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.

FORMULA

Conjectures from Colin Barker, Dec 20 2019: (Start)

G.f.: x^2*(17 - 10*x - 85*x^2 - 51*x^3 + 10*x^4 + 7*x^5) / ((1 + x)*(1 - 2*x - x^2)*(1 - 3*x - 2*x^2 + x^3)).

a(n) = 4*a(n-1) + 2*a(n-2) - 11*a(n-3) - 8*a(n-4) + a(n-5) + a(n-6) for n>7.

(End)

CROSSREFS

Sequence in context: A146453 A146046 A048508 * A029914 A058319 A095089

Adjacent sequences:  A020876 A020877 A020878 * A020880 A020881 A020882

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

a(6)-a(26) from Sean A. Irvine, May 01 2019

STATUS

approved

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Last modified August 4 01:53 EDT 2020. Contains 336201 sequences. (Running on oeis4.)