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 A331197 Number of nonnegative integer matrices with 2 distinct columns and any number of nonzero rows with each column sum being n and rows in nonincreasing lexicographic order. 3
 0, 1, 7, 28, 104, 332, 1032, 2983, 8384, 22622, 59479, 151902, 379616, 927521, 2224100, 5236410, 12130549, 27669296, 62229605, 138095206, 302672402, 655627183, 1404598865, 2977830134, 6251059210, 12999297747, 26791987616, 54750232180, 110977385294, 223204454700, 445590973235 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The condition that the rows be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of rows. LINKS Andrew Howroyd, Table of n, a(n) for n = 0..400 FORMULA a(n) = A002774(n) - A000041(n). EXAMPLE The a(2) = 7 matrices are:    [2 1]   [2 0]   [1 2]   [1 1]   [2 0]   [1 0]   [1 0]    [0 1]   [0 2]   [1 0]   [1 0]   [0 1]   [1 0]   [1 0]                            [0 1]   [0 1]   [0 2]   [0 1]                                                    [0 1] See the example in A331197 for the a(3) = 28 case. CROSSREFS Column k=2 of A331161. Cf. A000041, A002774, A331197. Sequence in context: A241400 A219411 A224404 * A024207 A000416 A000417 Adjacent sequences:  A331194 A331195 A331196 * A331198 A331199 A331200 KEYWORD nonn AUTHOR Andrew Howroyd, Jan 11 2020 STATUS approved

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Last modified August 17 15:35 EDT 2022. Contains 356189 sequences. (Running on oeis4.)