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Search: id:A095308
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| A095308 |
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Number of walks of length n between two nodes at distance 3 in the cycle graph C_7. |
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+0
2
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| 1, 1, 5, 6, 21, 28, 84, 121, 331, 507, 1300, 2093, 5110, 8568, 20129, 34885, 79477, 141494, 314489, 572264, 1246784, 2309385, 4950751, 9303411, 19684692, 37427313, 78354346, 150402700, 312168761, 603861897, 1244620149
(list; graph; listen)
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OFFSET
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3,3
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COMMENT
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In general 2^n/m*Sum(r,0,m-1,Cos(2Pi*k*r/m)Cos(2Pi*r/m)^n) is the number of walks of length n between two nodes at distance k in the cycle graph C_m. Here we have m=7 and k=3.
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FORMULA
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a(n)= 2^n/7*Sum(r, 0, 6, Cos(6Pi*r/7)Cos(2Pi*r/7)^n) G.f.: x^3/((-1+2x)(-1-x+2x^2+x^3)) a(n)=a(n-1)+4a(n-2)-3a(n-3)-2a(n-4)
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CROSSREFS
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Sequence in context: A057520 A060423 A037951 this_sequence A132796 A006492 A110344
Adjacent sequences: A095305 A095306 A095307 this_sequence A095309 A095310 A095311
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KEYWORD
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nonn
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AUTHOR
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Herbert Kociemba (kociemba(AT)t-online.de), Jul 03 2004
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