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%I #7 Aug 17 2015 14:43:13
%S 0,1,1,6,15,55,168,559,1785,5814,18755,60787,196560,636323,2058797,
%T 6663030,21561015,69774527,225792504,730684103,2364536625,7651812246,
%U 24761766811,80130789371,259308635040,839140445275,2715515402053
%N Jacobsthal(n)*Fibonacci(n).
%C 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.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,7,2,-4)
%F 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)).
%t LinearRecurrence[{1,7,2,-4},{0,1,1,6},30] (* _Harvey P. Dale_, Aug 17 2015 *)
%K easy,nonn
%O 0,4
%A _Paul Barry_, Mar 22 2004
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