A020879 Number of elementary edge-subgraphs in Moebius ladder M_n.

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

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