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A203151
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(n-1)-st elementary symmetric function of {1,1,2,2,3,3,4,4,5,5,...,Floor[(n+1)/2]}.
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1
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1, 2, 5, 12, 40, 132, 564, 2400, 12576, 65760, 408960, 2540160, 18299520, 131725440, 1079205120, 8836853760, 81157386240, 745047797760, 7582159872000, 77138417664000, 861690783744000, 9623448705024000, 117074735382528000
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..23.
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EXAMPLE
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Let esf abbreviate "elementary symmetric function". Then
0th esf of {2}: 1
1st esf of {1,1}: 1+1=2
2nd efs of {1,1,2} is 1*1+1*2+1*2=5
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MATHEMATICA
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f[k_] := Floor[(k + 1)/2]; t[n_] := Table[f[k], {k, 1, n}]
a[n_] := SymmetricPolynomial[n - 1, t[n]]
Table[a[n], {n, 1, 22}] (* A203151 *)
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CROSSREFS
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Cf. A203152.
Sequence in context: A050258 A051436 A054581 * A140440 A005664 A009739
Adjacent sequences: A203148 A203149 A203150 * A203152 A203153 A203154
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling, Dec 29 2011
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STATUS
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approved
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