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A173562
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a(n) = n^2 + floor(n/4).
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5
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0, 1, 4, 9, 17, 26, 37, 50, 66, 83, 102, 123, 147, 172, 199, 228, 260, 293, 328, 365, 405, 446, 489, 534, 582, 631, 682, 735, 791, 848, 907, 968, 1032, 1097, 1164, 1233, 1305, 1378, 1453, 1530, 1610, 1691, 1774, 1859, 1947, 2036, 2127, 2220, 2316, 2413, 2512
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = floor((n + 1/8)^2).
a(n) = 2*a(n-1) - a(n-2) + a(n-4) - 2*a(n-5) + a(n-6) for n>5.
G.f.: x*(1+2*x+2*x^2+3*x^3)/((1+x)*(x^2+1)*(1-x)^3). - R. J. Mathar, Feb 27 2010
a(n) = (8*n^2+2*n-3+i^(2*n)+(1+i)*i^(-n)+(1-i)*i^n)/8 where i=sqrt(-1). - Wesley Ivan Hurt, Jun 04 2016
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MAPLE
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MATHEMATICA
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Table[n^2+Floor[n/4], {n, 0, 50}] (* or *) LinearRecurrence[{2, -1, 0, 1, -2, 1}, {0, 1, 4, 9, 17, 26}, 50] (* Harvey P. Dale, Nov 25 2011 *)
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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
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AUTHOR
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STATUS
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approved
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