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 A001447 (5^n + 5^[ n/2 ] )/2. 3
 1, 3, 15, 65, 325, 1575, 7875, 39125, 195625, 976875, 4884375, 24415625, 122078125, 610359375, 3051796875, 15258828125, 76294140625, 381469921875, 1907349609375, 9536744140625, 47683720703125 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..300 Index entries for linear recurrences with constant coefficients, signature (5,5,-25). FORMULA a(0)=1, a(1)=3, a(2)=15, a(n)=5a(n-1)+5a(n-2)-25a(n-3) [From Harvey P. Dale, May 05 2011] G.f.: (1-2x-5x^2)/(1-5x-5x^2+25x^3) [From Harvey P. Dale, May 05 2011] MATHEMATICA Table[(5^n+5^Floor[n/2])/2, {n, 0, 20}] (* or *) LinearRecurrence[ {5, 5, -25}, {1, 3, 15}, 50](* Harvey P. Dale, May 05 2011 *) PROG (PARI) a(n)=(5^n+5^(n\2))/2 \\ Charles R Greathouse IV, Apr 17 2012 CROSSREFS Sequence in context: A080948 A098102 A144067 * A106732 A052981 A086200 Adjacent sequences:  A001444 A001445 A001446 * A001448 A001449 A001450 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified June 14 21:27 EDT 2021. Contains 345041 sequences. (Running on oeis4.)