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 A316974 Number of non-isomorphic strict multiset partitions of {1, 1, 2, 2, 3, 3, ..., n, n}. 15
 1, 1, 4, 14, 49, 173, 652, 2494 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Also the number of unlabeled multigraphs with n edges, allowing loops, spanning an initial interval of positive integers with no equivalent vertices (two vertices are equivalent if in every edge the multiplicity of the first is equal to the multiplicity of the second). For example, non-isomorphic representatives of the a(2) = 4 multigraphs are {(1,2),(1,3)}, {(1,1),(1,2)}, {(1,1),(2,2)}, {(1,1),(1,1)}. LINKS EXAMPLE Non-isomorphic representatives of the a(3) = 14 strict multiset partitions:   (112233),   (1)(12233), (11)(2233), (12)(1233), (112)(233),   (1)(2)(1233), (1)(12)(233), (1)(23)(123), (2)(11)(233), (11)(22)(33), (12)(13)(23),   (1)(2)(3)(123), (1)(2)(12)(33), (1)(2)(13)(23). CROSSREFS Cf. A001055, A007716, A007717, A007719, A020554, A020555, A045778, A050535, A053419, A061742, A094574, A162247, A316892, A316972. Sequence in context: A071737 A071741 A211305 * A278026 A001894 A215493 Adjacent sequences:  A316971 A316972 A316973 * A316975 A316976 A316977 KEYWORD nonn,more AUTHOR Gus Wiseman, Jul 17 2018 EXTENSIONS a(7) from Andrew Howroyd, Feb 07 2020 STATUS approved

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Last modified February 25 21:00 EST 2020. Contains 332258 sequences. (Running on oeis4.)