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A058878
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Triangle T(n,k) = number of labeled graphs of even degree with n nodes and k edges (n >= 0, 0<=k<=n(n-1)/2).
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0
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1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 4, 3, 0, 0, 1, 0, 0, 10, 15, 12, 15, 10, 0, 0, 1, 1, 0, 0, 20, 45, 72, 160, 240, 195, 120, 96, 60, 15, 0, 0, 0, 1, 0, 0, 35, 105, 252, 805, 1935, 3255, 4515, 5481, 5481, 4515, 3255, 1935, 805, 252, 105, 35, 0, 0, 1, 1, 0, 0, 56
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history;
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internal format)
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OFFSET
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0,14
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REFERENCES
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F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 13, (1.4.7).
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LINKS
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Table of n, a(n) for n=0..69.
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EXAMPLE
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1; 1,0; 1,0,0; 1,0,0,1; 1,0,0,4,3,0,0; ...
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MAPLE
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w := p->expand(simplify(2^(-p)*(1+x)^(p*(p-1)/2)*add(binomial(p, n)*( (1-x)/(1+x))^(n*(p-n)), n=0..p))); T := (n, k)->coeff(w(n), x, k);
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CROSSREFS
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Sequence in context: A057110 A073275 A030120 * A019983 A019984 A187765
Adjacent sequences: A058875 A058876 A058877 * A058879 A058880 A058881
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KEYWORD
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nonn,easy,nice,tabf
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AUTHOR
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N. J. A. Sloane, Jan 07 2001
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STATUS
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approved
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