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A093043
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Jacobsthal(n)*Fibonacci(n-1).
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1
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0, 0, 1, 3, 10, 33, 105, 344, 1105, 3591, 11594, 37565, 121485, 393264, 1272413, 4117971, 13325450, 43123017, 139547457, 451587592, 1461364025, 4729080015, 15303613546, 49523551333, 160261550085, 518617316448, 1678280815525
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Form a graph from a triangle and its midpoint triangle. A093043 counts walks of length n between two vertices of the original triangle.
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FORMULA
| G.f.: x^2(1+2x)/((1+x-x^2)(1-2x-4x^2)); a(n)=A001045(n)*A000045(n-1); a(n) := (2^n/3-(-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: A115240 A027989 A096483 * A061566 A082398 A053156
Adjacent sequences: A093040 A093041 A093042 * A093044 A093045 A093046
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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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