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A093042 Jacobsthal(n)*Fibonacci(n). 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

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.

LINKS

Table of n, a(n) for n=0..26.

Index entries for linear recurrences with constant coefficients, signature (1,7,2,-4)

FORMULA

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)).

MATHEMATICA

LinearRecurrence[{1, 7, 2, -4}, {0, 1, 1, 6}, 30] (* Harvey P. Dale, Aug 17 2015 *)

CROSSREFS

Sequence in context: A119132 A073065 A190801 * A270624 A270675 A271002

Adjacent sequences:  A093039 A093040 A093041 * A093043 A093044 A093045

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 22 2004

STATUS

approved

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Last modified February 26 09:20 EST 2020. Contains 332277 sequences. (Running on oeis4.)