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A173511
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a(n) = 4*n^2 + floor(n/2).
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7
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0, 4, 17, 37, 66, 102, 147, 199, 260, 328, 405, 489, 582, 682, 791, 907, 1032, 1164, 1305, 1453, 1610, 1774, 1947, 2127, 2316, 2512, 2717, 2929, 3150, 3378, 3615, 3859, 4112, 4372, 4641, 4917, 5202, 5494, 5795, 6103, 6420, 6744, 7077, 7417, 7766, 8122
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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) = floor((2*n + 1/8)^2).
a(n)= 2*a(n-1) -2*a(n-3) +a(n-4). G.f.: -x*(4+9*x+3*x^2)/((1+x)*(x-1)^3). - R. J. Mathar, Feb 21 2010
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EXAMPLE
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a(6) = 147; 4(6)^2 + floor(6/3) = 144 + 3 = 147.
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MAPLE
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MATHEMATICA
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LinearRecurrence[{2, 0, -2, 1}, {0, 4, 17, 37}, 50] (* Harvey P. Dale, Nov 23 2019 *)
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PROG
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(Python)
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CROSSREFS
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KEYWORD
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nonn,easy,changed
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AUTHOR
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STATUS
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approved
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