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 A003509 Let k(m) denote the least integer such that every m X m (0,1)-matrix with exactly k(m) ones in each row and in each column contains a 2 X 2 submatrix without zeros. The sequence gives the index n of the first term in each string of equal entries in the {k(m)} sequence (see A155934). (Formerly M0833) 2
 2, 3, 7, 13, 21, 31 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS E. T. Wang and R. K. Guy, Problem E2429, Amer. Math. Monthly, 81 (1974), 1112-1113. CROSSREFS Cf. A005991 (index of last term), A155934. Sequence in context: A325875 A049887 A048216 * A238432 A238423 A133370 Adjacent sequences:  A003506 A003507 A003508 * A003510 A003511 A003512 KEYWORD nonn,more AUTHOR EXTENSIONS Title made more specific by Sean A. Irvine, Jun 04 2015 STATUS approved

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Last modified January 21 05:39 EST 2020. Contains 331104 sequences. (Running on oeis4.)