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A098500
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Number of squares on infinite quarter chessboard at <=n knight moves from the corner.
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4
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1, 3, 12, 32, 59, 91, 130, 176, 229, 289, 356, 430, 511, 599, 694, 796, 905, 1021, 1144, 1274, 1411, 1555, 1706, 1864, 2029, 2201, 2380, 2566, 2759, 2959, 3166, 3380, 3601, 3829, 4064, 4306, 4555, 4811, 5074, 5344, 5621, 5905, 6196, 6494, 6799, 7111, 7430
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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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a(n) = (1/2) * (7*n^2 + n + 2), for n>3.
G.f.: -(2*x^6-2*x^5-4*x^4+4*x^3+6*x^2+1) / (x-1)^3. - Colin Barker, Jul 15 2013
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EXAMPLE
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3 squares are reachable after 1 move, from these you can reach 8 new squares more, so a(1)=3, a(2)=12.
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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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