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 A217990 Size of largest semigroup generated by one boolean n X n matrix. 0
 1, 2, 5, 10, 17, 26, 37, 50, 65, 82, 101, 122, 145, 170, 197, 226, 257, 290, 420 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES J. Denes, K. H. Kim, and F. W. Roush, Automata on one symbol, in Studies in Pure Mathematics: To the Memory of Paul Turan, Birkhauser, 1983, pp. 127-134. LINKS George Markowsky, Bounds on the index and period of a binary relation on a finite set, Semigroup Forum 13 (1977), 253-259. FORMULA For n < 19, a(n) = n^2 - 2n + 2.  For large n, l(n) <= a(n) < n^2 - 2n + 2 + l(n), where l(n) is Landau's function (A000793).  It seems the exact value is still unknown. EXAMPLE a(4) = 10: the matrix [[0,0,0,1], [0,0,1,0], [1,0,0,0], [0,1,1,0]] generates a semigroup of order 10 under boolean matrix multiplication. CROSSREFS Cf. A000793, A202140. Sequence in context: A303372 A159547 A002522 * A300164 A248193 A069987 Adjacent sequences:  A217987 A217988 A217989 * A217991 A217992 A217993 KEYWORD nonn,hard,more AUTHOR Jeffrey Shallit, Oct 17 2012 STATUS approved

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Last modified October 15 05:14 EDT 2018. Contains 316202 sequences. (Running on oeis4.)