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A093044
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A Jacobsthal Fibonacci product.
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1
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1, 0, 2, 2, 12, 30, 110, 336, 1118, 3570, 11628, 37510, 121574, 393120, 1272646, 4117594, 13326060, 43122030, 139549054, 451585008, 1461368206, 4729073250, 15303624492, 49523533622, 160261578742, 518617270080, 1678280890550
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Form a graph from a triangle and its midpoint triangle. A093044 counts closed walks of length n at a vertex of the original triangle.
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FORMULA
| G.f.: (1-x-5x^2-2x^3)/((1+x-x^2)(1-2x-4x^2)); a(n)=A078008(n)*A000045(n-1); a(n)=(2^n/3+2(-1)^n/3)(((1+sqrt(5))/2)^(n-1)/sqrt(5)-((1-sqrt(5))/2)^(n-1)/sqrt(5)).
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CROSSREFS
| Sequence in context: A052612 A130306 A199127 * A151366 A184944 A033886
Adjacent sequences: A093041 A093042 A093043 * A093045 A093046 A093047
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Mar 22 2004
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