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Number of vertex cuts in the n-Möbius ladder.
0

%I #15 Apr 22 2023 00:47:09

%S 0,0,8,82,512,2644,12364,54598,232772,970520,3988624,16239066,

%T 65709256,264814140,1064414100,4271035662,17118683020,68563527616,

%U 274481537112,1098506723042,4395504614544,17585769696164,70352578566620,281434319454038,1125797816327892

%N Number of vertex cuts in the n-Möbius ladder.

%C Sequence extended to n = 1 using formula.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/MoebiusLadder.html">Moebius Ladder</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/VertexCut.html">Vertex Cut</a>

%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (10,-35,48,-11,-22,7,4).

%F a(n) = 2^(2*n) - A286185(n) - 1. - _Pontus von Brömssen_, Aug 30 2022

%F a(n) = 4^n + n - LucasL(n, 2) - 3*n*Fibonacci(n, 2).

%F a(n) = 10*a(n-1) - 35*a(n-2) + 48*a(n-3) - 11*a(n-4) - 22*a(n-5) + 7*a(n-6) + 4*a(n-7).

%F G.f.: 2*x^3*(-4-x+14*x^2-5*x^3+2*x^4)/((-1+x)^2*(-1+4*x)*(-1+2*x+x^2)^2).

%t Table[4^n + n - LucasL[n, 2] - 3 n Fibonacci[n, 2], {n, 20}]

%t LinearRecurrence[{10, -35, 48, -11, -22, 7, 4}, {0, 0, 8, 82, 512, 2644, 12364}, 20]

%t CoefficientList[Series[2 x^2 (-4 - x + 14 x^2 - 5 x^3 + 2 x^4)/((-1 + x)^2 (-1 + 4 x) (-1 + 2 x + x^2)^2), {x, 0, 20}], x]

%Y Cf. A286185.

%K nonn

%O 1,3

%A _Eric W. Weisstein_, Aug 30 2022

%E More terms from _Pontus von Brömssen_, Aug 30 2022