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A093045
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2*Jacobsthal(n-1)*Fibonacci(n).
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1
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0, 0, 2, 4, 18, 50, 176, 546, 1806, 5780, 18810, 60698, 196704, 636090, 2059174, 6662420, 21562002, 69772930, 225795088, 730679922, 2364543390, 7651801300, 24761784522, 80130760714, 259308681408, 839140370250, 2715515523446
(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. A093045 counts walks of length n between a vertex of the original triangle and the opposite vertex of the midpoint triangle.
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FORMULA
| G.f.: 2x^2(1+x)/((1+x-x^2)(1-2x-4x^2)); a(n)=2*A001045(n-1)*A000045(n); a(n)=2(2^n/6+(-1)^n/3)(((1+sqrt(5))/2)^n/sqrt(5)-((1-sqrt(5))/2)^n/sqrt(5)).
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CROSSREFS
| Sequence in context: A151449 A045664 A106520 * A083694 A179040 A009679
Adjacent sequences: A093042 A093043 A093044 * A093046 A093047 A093048
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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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