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A007081 Number of labeled Eulerian oriented graphs with n nodes.
(Formerly M3009)
3
1, 1, 3, 15, 219, 7839, 777069, 208836207, 156458382975, 328208016021561, 1946879656265710431, 32834193098697741359313, 1582809785794578499063205301, 218989607557709869788340418432175, 87269441106898007902526099850864517077 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
B. D. McKay, Applications of a technique for labeled enumeration, Congress. Numerantium, 40 (1983), 207-221.
FORMULA
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
CROSSREFS
Sequence in context: A264705 A117820 A126453 * A126455 A136466 A296856
KEYWORD
nonn,nice
AUTHOR
STATUS
approved

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Last modified March 28 21:57 EDT 2024. Contains 371254 sequences. (Running on oeis4.)