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0, 1, 3, 8, 14, 23, 33, 46, 60, 77, 95, 116, 138, 163, 189, 218, 248, 281, 315, 352, 390, 431, 473, 518, 564, 613, 663, 716, 770, 827, 885, 946, 1008, 1073, 1139, 1208, 1278, 1351, 1425, 1502, 1580, 1661, 1743, 1828, 1914, 2003, 2093, 2186, 2280, 2377, 2475
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Quasipolynomial of order 2. [Charles R Greathouse IV, Jan 19 2012]
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (2,0,-2,1).
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FORMULA
| G.f.: x*(1+x+2*x^2)/((1-x)^2*(1-x^2)).
a(n) = (2*n*(2*n-1)-(-1)^n+1)/4. - Bruno Berselli, Feb 17 2011
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MATHEMATICA
| Table[n^2-Floor[n/2], {n, 0, 100}] (* From Vladimir Joseph Stephan Orlovsky, Apr 12 2011 *)
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PROG
| (PARI) a(n)=n^2-n\2
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CROSSREFS
| Cf. A033991(n)=a(2n). A033951(n)=a(2n+1).
Sequence in context: A062550 A022947 A098762 * A140479 A146158 A062354
Adjacent sequences: A014845 A014846 A014847 * A014849 A014850 A014851
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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