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A250102
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a(n) = 2*5^n - (1+2i)^(2n) - (1-2i)^(2n) where i = sqrt(-1).
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2
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0, 16, 64, 16, 2304, 5776, 7744, 309136, 451584, 2062096, 38837824, 27920656, 424030464, 4570300816, 1039933504, 74815378576, 501671890944, 2396689936, 11857885086784, 50863084730896, 8725926945024, 1727825132557456, 4673690093529664, 5056176437385616, 234290415599944704
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: 16*x*(1 + 5*x) / ((1 - 5*x)*(1 + 6*x + 25*x^2)).
a(n) = -a(n-1) + 5*a(n-2) + 125*a(n-3) for n>2.
(End)
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MATHEMATICA
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Array[2*5^# - (1 + 2 I)^(2 #) - (1 - 2 I)^(2 #) &, 25, 0] (* Michael De Vlieger, Jun 19 2018 *)
LinearRecurrence[{-1, 5, 125}, {0, 16, 64}, 30] (* Harvey P. Dale, May 26 2020 *)
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PROG
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(PARI) a(n) = 2*5^n - (1+2*I)^(2*n) - (1-2*I)^(2*n) \\ Michel Marcus, Aug 28 2015
(PARI) concat(0, Vec(16*x*(1 + 5*x) / ((1 - 5*x)*(1 + 6*x + 25*x^2)) + O(x^30))) \\ Colin Barker, Feb 20 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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