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A308111 Isomorphism classes of Eulerian digraphs with n vertices, allowing loops. 5
1, 2, 6, 24, 160, 2512, 129816, 22665792, 13056562208, 24953006054144, 160860329639968800, 3555065836569542246400, 273147301191314006316868352, 73832333258502021627712839197696, 70920540648597652305602460997787710080, 244186544390677638132290202415190606165938176, 3036252267734950687777830287721323374283100639476736 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Eulerian means that for every vertex the in-degree equals the out-degree.
LINKS
FORMULA
Euler transform of A308128.
EXAMPLE
For n=2 the a(2)=6 solutions are: two non-adjacent vertices with or without loops (3 cases), two vertices with or without loops connected by edges in each direction (3 cases).
CROSSREFS
For labeled digraphs rather than isomorphism classes see A229865.
For isomorphism classes with loops forbidden see A058338.
Cf. A308128 (connected version of this).
Sequence in context: A012715 A038205 A012361 * A121773 A304996 A012711
KEYWORD
nonn,hard
AUTHOR
Brendan McKay, May 11 2019
EXTENSIONS
Terms a(10) and beyond from Andrew Howroyd, Apr 12 2020
STATUS
approved

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Last modified July 16 14:52 EDT 2024. Contains 374349 sequences. (Running on oeis4.)