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 A331704 Number of nonnegative integer matrices with n distinct columns and any number of distinct nonzero rows with column sums 2 and columns in decreasing lexicographic order. 3
 1, 1, 6, 46, 544, 7983, 144970, 3097825, 76494540, 2139610590, 66898897827, 2311748912745, 87494097274959, 3599356204576335, 159917091369687135, 7631292367127171222, 389282192196378927707, 21138914821756778420757, 1217459545430430305769230 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The condition that the columns be in decreasing order is equivalent to considering nonequivalent matrices with distinct columns up to permutation of columns. LINKS Andrew Howroyd, Table of n, a(n) for n = 0..200 FORMULA a(n) = (1/n!)*Sum_{k=0..n} Stirling1(n, k) * A331644(k). EXAMPLE The a(2) = 6 matrices are:    [1 1]  [1 0]  [1 0]  [2 1]  [2 0]  [1 0]    [1 0]  [1 1]  [0 1]  [0 1]  [0 2]  [1 2]    [0 1]  [0 1]  [1 1] CROSSREFS Row n=2 of A331570. Cf. A331644, A331705. Sequence in context: A326324 A215084 A232058 * A275031 A094655 A327364 Adjacent sequences:  A331701 A331702 A331703 * A331705 A331706 A331707 KEYWORD nonn AUTHOR Andrew Howroyd, Jan 25 2020 STATUS approved

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Last modified December 1 16:29 EST 2021. Contains 349430 sequences. (Running on oeis4.)