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 A229865 Number of n X n 0..1 arrays with corresponding row and column sums equal. 9
 1, 2, 8, 80, 2432, 247552, 88060928, 112371410944, 523858015518720, 9041009511609073664, 583447777113052431515648, 141885584718620229407228821504, 130832005909904417592540055577034752, 459749137931232137234615429529864283095040, 6182706200522446492946534924719926752508110700544 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Also known as labeled Eulerian digraphs allowing loops. - Brendan McKay, May 12 2019 LINKS FORMULA a(n) = 2^n * A007080(n). - Andrew Howroyd, Sep 11 2019 EXAMPLE Some solutions for n=4:   0 0 0 1     0 0 1 0     0 0 0 1     0 0 1 0     0 0 1 1   0 1 0 0     1 0 0 0     1 0 1 0     0 0 1 1     1 0 0 1   0 0 0 1     0 1 0 0     0 1 0 1     0 1 1 1     1 1 1 0   1 0 1 0     0 0 0 1     0 1 1 0     1 1 0 0     0 1 1 1 From Gus Wiseman, Jun 22 2019: (Start) The a(3) = 8 Eulerian digraph edge-sets:   {}   {11}   {22}   {11,22}   {12,21}   {11,12,21}   {12,21,22}   {11,12,21,22} (End) MATHEMATICA Table[Length[Select[Subsets[Tuples[Range[n], 2]], Sort[First/@#]==Sort[Last/@#]&]], {n, 4}] (* Gus Wiseman, Jun 22 2019 *) CROSSREFS Column 1 of A229870. The unlabeled version is A308111. Cf. A000595, A002416, A002720, A007080. Cf. A326209, A326237, A326251, A326252, A326253. Sequence in context: A289897 A134054 A323716 * A134086 A297566 A013175 Adjacent sequences:  A229862 A229863 A229864 * A229866 A229867 A229868 KEYWORD nonn AUTHOR R. H. Hardin, Oct 01 2013 EXTENSIONS a(0)=1 prepended by Alois P. Heinz, May 14 2019 Terms a(11) and beyond from Andrew Howroyd, Sep 11 2019 STATUS approved

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Last modified October 20 22:37 EDT 2019. Contains 328291 sequences. (Running on oeis4.)