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 A260340 Triangle read by rows: T(n,k) = number of sets of linear n-ads in k variables. 6
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 6, 1, 1, 1, 1, 22, 22, 1, 1, 1, 1, 130, 550, 130, 1, 1, 1, 1, 822, 16700, 16700, 822, 1, 1, 1, 1, 6202, 703297, 3330915, 703297, 6202, 1, 1, 1, 1, 52552, 38135272, 957659906, 957659906, 38135272, 52552, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,13 COMMENTS T(n,k) is the number of nonequivalent n X n binary matrices with k ones in every row and column up to permutation of rows. - Andrew Howroyd, Apr 18 2020 LINKS Andrew Howroyd, Table of n, a(n) for n = 0..230 (rows 0..20) P. A. MacMahon, Combinations derived from m identical sets of n different letters and their connexion with general magic squares, Proc. London Math. Soc., 17 (1917), 25-41. FORMULA T(n,k) = T(n,n-k). - Andrew Howroyd, Apr 18 2020 EXAMPLE Triangle begins: 1; 1, 1; 1, 1, 1; 1, 1, 1, 1; 1, 1, 6, 1, 1; 1, 1, 22, 22, 1, 1; 1, 1, 130, 550, 130, 1, 1; 1, 1, 822, 16700, 16700, 822, 1, 1; 1, 1, 6202, 703297, 3330915, 703297, 6202, 1, 1; ... CROSSREFS Columns k=0..4 are A000012, A000012, A002137, A333899, A333900. Row sums are A333891. Cf. A008300, A133687, A257463. Sequence in context: A339747 A293901 A324891 * A040037 A344877 A356156 Adjacent sequences: A260337 A260338 A260339 * A260341 A260342 A260343 KEYWORD nonn,tabl AUTHOR N. J. A. Sloane, Jul 30 2015 EXTENSIONS Extended to include k=0 and more terms added by Andrew Howroyd, Apr 18 2020 STATUS approved

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Last modified September 8 17:50 EDT 2024. Contains 375753 sequences. (Running on oeis4.)