A078469 Number of different compositions of the ladder graph L_n.
1, 2, 12, 74, 456, 2810, 17316, 106706, 657552, 4052018, 24969660, 153869978, 948189528, 5843007146, 36006232404, 221880401570, 1367288641824, 8425612252514, 51920962156908, 319951385193962, 1971629273320680
Offset: 0
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..200
- Liam Buttitta, On the Number of Compositions of Km X Pn, Journal of Integer Sequences, Vol. 25 (2022), Article 22.4.1.
- Tomislav Došlić and Luka Podrug, Sweet division problems: from chocolate bars to honeycomb strips and back, arXiv:2304.12121 [math.CO], 2023.
- Tanya Khovanova, Recursive Sequences
- A. Knopfmacher and M. E. Mays, Graph Compositions. I: Basic Enumeration, Integers 1(2001), #A04.
- J. N. Ridley and M. E. Mays, Compositions of unions of graphs, Fib. Quart., 42 (2004), 222-230.
- Index entries for linear recurrences with constant coefficients, signature (6,1).
Crossrefs
Programs
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Magma
I:=[1, 2, 12]; [n le 3 select I[n] else 6*Self(n-1)+Self(n-2): n in [1..30]]; // Vincenzo Librandi, May 17 2013
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Mathematica
Join[{1},LinearRecurrence[{6,1},{2,12},30]] (* Harvey P. Dale, Jul 22 2013 *)
Formula
a(n) = 6*a(n-1) + a(n-2).
G.f.: 1 + 2*x/(1 - 6*x - x^2).
a(n) = ((3 + s)^n - (3 - s)^n)/s, where s = sqrt(10) (assumes a(0) = 0).
Asymptotic to (3 + sqrt(10))^n/sqrt(10). - Ralf Stephan, Jan 03 2003
Let p[i] = Fibonacci(3*i) and A be the Hessenberg matrix of order n defined by: A[i,j] = p[j-i+1], if i <= j; A[i,j] = -1, if i = j + 1; and A[i,j] = 0, otherwise. Then, for n >= 1, a(n) = det(A). - Milan Janjic, May 08 2010
a(n) = 2*A005668(n), n > 0. - R. J. Mathar, Nov 29 2015
a(n) >= A116694(2,n). - R. J. Mathar, Nov 29 2015
Extensions
a(0) changed from 0 to 1 by N. J. A. Sloane, Sep 21 2009, at the suggestion of Hugo van der Sanden
Comments