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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 Table of n, a(n) for n=0..16. Gus Wiseman, Non-isomorphic representatives of the a(3) = 24 Eulerian digraphs with loops. 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). Cf. A000273, A000595, A002416, A002720, A308161. Sequence in context: A012715 A038205 A012361 * A121773 A304996 A012711 Adjacent sequences: A308108 A308109 A308110 * A308112 A308113 A308114 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.)