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 A213434 Number of n X n symmetric binary matrices with zero diagonal and no three-node loops x(i,j)*x(j,k)*x(k,i) = 1, i < j < k. 0
 1, 2, 7, 41, 388, 5789, 133501, 4682270, 246348115, 19213627145, 2198376297964, 365587270414697, 87628189849380625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Equivalently, number of triangle-free labeled graphs on n vertices. - Falk Hüffner, Jun 19 2018 LINKS F. Hüffner, tinygraph, software for generating integer sequences based on graph properties, version 8c665c7 EXAMPLE Some solutions for n=4:   0 1 0 0     0 1 1 0     0 1 0 0     0 0 1 1     0 1 0 0   1 0 1 0     1 0 0 1     1 0 0 0     0 0 1 0     1 0 0 1   0 1 0 1     1 0 0 1     0 0 0 1     1 1 0 0     0 0 0 0   0 0 1 0     0 1 1 0     0 0 1 0     1 0 0 0     0 1 0 0 CROSSREFS Sequence in context: A047864 A173916 A163921 * A008934 A084871 A122942 Adjacent sequences:  A213431 A213432 A213433 * A213435 A213436 A213437 KEYWORD nonn,more AUTHOR R. H. Hardin, Jun 11 2012 EXTENSIONS a(11)-a(13) added using tinygraph by Falk Hüffner, Jun 19 2018 STATUS approved

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Last modified February 16 12:48 EST 2019. Contains 320163 sequences. (Running on oeis4.)