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A090727
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a(n) = 16a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 16.
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2
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2, 16, 254, 4048, 64514, 1028176, 16386302, 261152656, 4162056194, 66331746448, 1057145886974, 16848002445136, 268510893235202, 4279326289318096, 68200709735854334, 1086932029484351248, 17322711762013765634, 276076456162735898896
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OFFSET
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0,1
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COMMENTS
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Numbers n such that (n^2-4)/7 is a square. - Colin Barker, Mar 17 2014
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LINKS
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FORMULA
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a(n) = (8+sqrt(63))^n + (8-sqrt(63))^n.
a(n)^2 = a(2n) + 2.
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MATHEMATICA
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a[0] = 2; a[1] = 16; a[n_] := 16a[n - 1] - a[n - 2]; Table[ a[n], {n, 0, 15}] (* Robert G. Wilson v, Jan 30 2004 *)
LinearRecurrence[{16, -1}, {2, 16}, 20] (* T. D. Noe, Mar 17 2014 *)
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PROG
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(Sage) [lucas_number2(n, 16, 1) for n in range(0, 20)] # Zerinvary Lajos, Jun 26 2008
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Nikolay V. Kosinov (kosinov(AT)unitron.com.ua), Jan 18 2004
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EXTENSIONS
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STATUS
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approved
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