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A007081
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Number of labeled Eulerian oriented graphs with n nodes.
(Formerly M3009)
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3
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1, 1, 3, 15, 219, 7839, 777069, 208836207, 156458382975, 328208016021561, 1946879656265710431, 32834193098697741359313, 1582809785794578499063205301, 218989607557709869788340418432175, 87269441106898007902526099850864517077
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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a(n) = coefficient of [x_1*x_2*...*x_n]^(n-1) in Product_{1<=i<j<=n} (x_i^2 + x_j^2 + x_i*x_j). - Sean A. Irvine, Oct 08 2017
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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STATUS
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approved
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