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A228920
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Number of solutions to Sum_{i=1..n} x_i^2 == 0 (mod 4) with x_i in 0..3.
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9
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2, 4, 8, 32, 192, 1024, 4608, 18432, 69632, 262144, 1015808, 4063232, 16515072, 67108864, 270532608, 1082130432, 4311744512, 17179869184, 68585259008, 274341036032, 1098437885952, 4398046511104, 17600775979008, 70403103916032, 281543696187392
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OFFSET
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1,1
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LINKS
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FORMULA
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G.f.: -2*x*(12*x^2-6*x+1) / ((4*x-1)*(8*x^2-4*x+1)). - Colin Barker, Nov 10 2014
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MATHEMATICA
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Table[((2 + 2I)^n + (2 - 2I)^n + 4^n)/4, {n, 1, 30}]
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PROG
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(PARI) Vec(-2*x*(12*x^2-6*x+1)/((4*x-1)*(8*x^2-4*x+1)) + O(x^100)) \\ Colin Barker, Nov 10 2014
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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