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A109499
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Number of closed walks of length n on the complete graph on 5 nodes from a given node.
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16
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1, 0, 4, 12, 52, 204, 820, 3276, 13108, 52428, 209716, 838860, 3355444, 13421772, 53687092, 214748364, 858993460, 3435973836, 13743895348, 54975581388, 219902325556, 879609302220, 3518437208884, 14073748835532
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OFFSET
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0,3
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..1000
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FORMULA
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G.f. = (-1 + 3*z)/(-1 + 3*z + 4*z^2)
a(n) = (4^n + 4*(-1)^n)/5
a(n+1) = 4*A015521(n). - Paul Curtz, Nov 01 2009
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MATHEMATICA
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k=0; lst={k}; Do[k=4^n-k; AppendTo[lst, k], {n, 1, 5!}]; lst [From Vladimir Orlovsky, Dec 11 2008]
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PROG
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(MAGMA) [(4^n + 4*(-1)^n)/5: n in [0..30]]; // Vincenzo Librandi, Aug 12 2011
(PARI) a(n)=(4^n+4*(-1)^n)/5 \\ Charles R Greathouse IV, Oct 01 2012
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CROSSREFS
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Cf. A109502.
Cf. A001045, A078008, A097073, A115341, A015518, A054878, A015521 (forms k=4^n-k) [From Vladimir Orlovsky, Dec 11 2008]
Sequence in context: A149410 A149411 A149412 * A188230 A124006 A215524
Adjacent sequences: A109496 A109497 A109498 * A109500 A109501 A109502
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KEYWORD
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nonn,easy,walk
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AUTHOR
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Mitch Harris, Jun 30 2005
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EXTENSIONS
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Corrected by Franklin T. Adams-Watters, Sep 18 2006
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STATUS
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approved
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