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 A331316 Number of nonnegative integer matrices with n distinct columns and any number of distinct nonzero rows with each column sum being 2 and rows in decreasing lexicographic order. 3
 1, 1, 4, 27, 266, 3599, 62941, 1372117, 36248765, 1135864306, 41501271477, 1743624004536, 83268125043937, 4476101995389591, 268589319338401864, 17860954789864760357, 1307982591075162739660, 104895999816356419875935, 9166919404389461922512723 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The condition that the rows be in decreasing order is equivalent to considering nonequivalent matrices with distinct rows up to permutation of rows. LINKS Andrew Howroyd, Table of n, a(n) for n = 0..200 FORMULA a(n) = Sum_{k=0..n} Stirling1(n,k)*A094574(k). EXAMPLE The a(2) = 4 matrices are:    [2 1]   [2 0]   [1 2]   [1 1]    [0 1]   [0 2]   [1 0]   [1 0]                            [0 1] CROSSREFS Row n=2 of A331160. Cf. A094574. Sequence in context: A052813 A218653 A121353 * A265270 A161633 A052871 Adjacent sequences:  A331313 A331314 A331315 * A331317 A331318 A331319 KEYWORD nonn AUTHOR Andrew Howroyd, Jan 13 2020 STATUS approved

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Last modified September 16 07:19 EDT 2021. Contains 347469 sequences. (Running on oeis4.)