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A096019
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a(0)=3, a(n) = 3*a(n-1) + 2*(-1)^n.
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1
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3, 7, 23, 67, 203, 607, 1823, 5467, 16403, 49207, 147623, 442867, 1328603, 3985807, 11957423, 35872267, 107616803, 322850407, 968551223, 2905653667, 8716961003, 26150883007, 78452649023, 235357947067, 706073841203, 2118221523607
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OFFSET
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0,1
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COMMENTS
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The number of Pythagorean quadruples mod 3^n is given by a(n) 3^(2n-1). See A096018.
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LINKS
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FORMULA
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a(n) = 3^(n+1)-(3^n-(-1)^n)/2.
a(n) = 2*a(n-1)+3*a(n-2). G.f.: (3+x)/((1+x)*(1-3*x)). [Colin Barker, Mar 26 2012]
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MATHEMATICA
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LinearRecurrence[{2, 3}, {3, 7}, 30] (* Harvey P. Dale, Feb 10 2024 *)
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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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STATUS
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approved
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