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A093042
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Jacobsthal(n)*Fibonacci(n).
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3
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0, 1, 1, 6, 15, 55, 168, 559, 1785, 5814, 18755, 60787, 196560, 636323, 2058797, 6663030, 21561015, 69774527, 225792504, 730684103, 2364536625, 7651812246, 24761766811, 80130789371, 259308635040, 839140445275, 2715515402053
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OFFSET
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0,4
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COMMENTS
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Form a graph from a triangle and its midpoint triangle. A093042 counts walks of length n between a vertex of the original triangle and an adjacent vertex of the midpoint triangle.
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LINKS
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FORMULA
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G.f.: (1-2x^2)/((1+x-x^2)(1-2x-4x^2)); a(n)=A001045(n)*A000045(n); a(n) := (2^n/3-(-1)^n/3)(((1+sqrt(5))/2)^n/sqrt(5)-((1-sqrt(5))/2)^n/sqrt(5)).
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MATHEMATICA
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LinearRecurrence[{1, 7, 2, -4}, {0, 1, 1, 6}, 30] (* Harvey P. Dale, Aug 17 2015 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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