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Jacobsthal(n)*Fibonacci(n-1).
1

%I #5 Jun 13 2015 00:51:19

%S 0,0,1,3,10,33,105,344,1105,3591,11594,37565,121485,393264,1272413,

%T 4117971,13325450,43123017,139547457,451587592,1461364025,4729080015,

%U 15303613546,49523551333,160261550085,518617316448,1678280815525

%N Jacobsthal(n)*Fibonacci(n-1).

%C Form a graph from a triangle and its midpoint triangle. A093043 counts walks of length n between two vertices of the original 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.: x^2(1+2x)/((1+x-x^2)(1-2x-4x^2));

%F a(n)=A001045(n)*A000045(n-1);

%F a(n) := (2^n/3-(-1)^n/3)(((1+sqrt(5))/2)^(n-1)/sqrt(5)-((1-sqrt(5))/2)^(n-1)/sqrt(5)).

%K easy,nonn

%O 0,4

%A _Paul Barry_, Mar 22 2004