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A001447
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(5^n + 5^[ n/2 ] )/2.
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2
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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; internal format)
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OFFSET
| 0,2
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..300
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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]
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MATHEMATICA
| Table[(5^n+5^Floor[n/2])/2, {n, 0, 20}] (* or *) LinearRecurrence[ {5, 5, -25}, {1, 3, 15}, 50](* From Harvey P. Dale, May 05 2011 *)
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CROSSREFS
| Sequence in context: A080948 A098102 A144067 * A106732 A052981 A086200
Adjacent sequences: A001444 A001445 A001446 * A001448 A001449 A001450
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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