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A053439
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Expansion of (1+x+2*x^3)/((1-x)*(1-x^2)^2).
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0
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1, 2, 4, 8, 11, 18, 22, 32, 37, 50, 56, 72, 79, 98, 106, 128, 137, 162, 172, 200, 211, 242, 254, 288, 301, 338, 352, 392, 407, 450, 466, 512, 529, 578, 596, 648, 667, 722, 742, 800, 821, 882, 904, 968, 991, 1058, 1082, 1152, 1177, 1250, 1276
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| Even: a(2*n)= 2* n^2 +n +1, odd: a(2*n-1)= 2* n^2. - Frank Ellermann, Feb 11, 2002
a(n)=sum{k=0..n, C(n, mod(k, 2)) } - Paul Barry (pbarry(AT)wit.ie), Jul 24 2003
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MATHEMATICA
| CoefficientList[Series[(1+x+2x^3)/((1-x)(1-x^2)^2), {x, 0, 50}], x] (* or *)
LinearRecurrence[{1, 2, -2, -1, 1}, {1, 2, 4, 8, 11}, 50] (* From Harvey P. Dale, Apr 26 2011 *)
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CROSSREFS
| Sequence in context: A010068 A120632 A007295 * A180379 A033956 A159693
Adjacent sequences: A053436 A053437 A053438 * A053440 A053441 A053442
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jan 12 2000
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