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A101502 Number of closed walks on C_5 tensor J_2. 1
1, 0, 4, 0, 48, 32, 640, 896, 8960, 18432, 130048, 337920, 1941504, 5857280, 29605888, 98435072, 458424320, 1624375296, 7174881280, 26507476992, 113123524608, 429538672640, 1792440008704, 6929367695360, 28495396732928 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
Let (C_5 tensor J_2) be the 10 node graph whose adjacency matrix is the tensor product of that of C_5 and J_2=[1,1;1,1]. Then a(n) counts closed walks of length n at a vertex of the graph.
REFERENCES
E.R. van Dam, Graphs with few eigenvalues, Tilburg, 1968, p53.
LINKS
FORMULA
G.f.: (1-2x-8x^2+8x^3)/((1-4x)(1+2x-4x^2)); a(n)=2a(n-1)+12a(n-2)-16a(n-3), n>4; a(n)=(sqrt(5)-1)^n/5+(-sqrt(5)-1)^n/5+4^n/10+0^n/2.
(1/10) [4^n - (-2)^(n+1)*Lucas(n) ], n>0. - Ralf Stephan, May 16 2007
a(n)= 2^n*A052964(n-2), n>0. - R. J. Mathar, Mar 08 2021
CROSSREFS
Cf. A101501.
Sequence in context: A189424 A009371 A248952 * A118440 A247119 A296439
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Dec 04 2004
STATUS
approved

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Last modified July 22 14:00 EDT 2024. Contains 374499 sequences. (Running on oeis4.)