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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

Table of n, a(n) for n=2..7.

E. T. Wang and R. K. Guy, Problem E2429, Amer. Math. Monthly, 81 (1974), 1112-1113.

Index entries for sequences related to binary matrices

CROSSREFS

Cf. A005991 (index of last term), A155934.

Sequence in context: A070754 A049887 A048216 * A238432 A238423 A133370

Adjacent sequences:  A003506 A003507 A003508 * A003510 A003511 A003512

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Title made more specific by Sean A. Irvine, Jun 04 2015

STATUS

approved

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Last modified January 17 05:26 EST 2019. Contains 319207 sequences. (Running on oeis4.)