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A006100
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Gaussian binomial coefficient [ n,2 ] for q=3.
(Formerly M4912)
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9
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1, 13, 130, 1210, 11011, 99463, 896260, 8069620, 72636421, 653757313, 5883904390, 52955405230, 476599444231, 4289397389563, 38604583680520, 347441274648040, 3126971536402441
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OFFSET
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2,2
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REFERENCES
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J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.
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LINKS
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FORMULA
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G.f.: x^2/[(1-x)(1-3x)(1-9x)].
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MAPLE
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a:=n->sum((9^(n-j)-3^(n-j))/6, j=0..n): seq(a(n), n=1..17); # Zerinvary Lajos, Jan 15 2007
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MATHEMATICA
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f[k_] := 3^(k - 1); t[n_] := Table[f[k], {k, 1, n}]
a[n_] := SymmetricPolynomial[2, t[n]]
Table[a[n], {n, 2, 32}] (* A203243 *)
Table[a[n]/3, {n, 2, 32}] (* A006100 *)
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PROG
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(Sage) [gaussian_binomial(n, 2, 3) for n in range(2, 19)] # Zerinvary Lajos, May 25 2009
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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