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 A333888 Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 3 up to permutations of rows and columns. 1
 1, 1, 2, 5, 12, 29, 79, 225, 677, 2141, 7121, 24693, 89117, 333312, 1288949, 5140039, 21094565, 88931387, 384544989, 1703083332, 7715920544, 35720666818, 168809971994, 813633173238, 3996247863791, 19986651995983, 101715962631912, 526405121697307, 2768690275913665, 14791474244527076, 80224577967948446 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS EXAMPLE The a(2) = 2 matrices are:   [0 3]  [1 2]   [3 0]  [2 1] CROSSREFS Column k=3 of A333737. Sequence in context: A132807 A261234 A324787 * A228516 A101411 A042789 Adjacent sequences:  A333885 A333886 A333887 * A333889 A333890 A333891 KEYWORD nonn AUTHOR Andrew Howroyd, Apr 08 2020 STATUS approved

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Last modified May 23 09:39 EDT 2022. Contains 353975 sequences. (Running on oeis4.)