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A178464 Minimal number of lines that must be removed from an n X n square array of cells in order to break all rectangles. 0
1, 3, 7, 11, 18, 25, 34, 43, 55, 67, 82, 97 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

See Gardner for precise definition.

REFERENCES

M. Gardner, Mathematical Carnival, Random House, NY, 1975; page 120.

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

To illustrate a(2) = 3: remove edges A, B and C:

--A----

|  |  |

-----B-

|  C  |

-------

CROSSREFS

Sequence in context: A210977 A049792 A062851 * A071979 A335323 A097748

Adjacent sequences:  A178461 A178462 A178463 * A178465 A178466 A178467

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 23 2010

STATUS

approved

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Last modified August 4 12:54 EDT 2020. Contains 336201 sequences. (Running on oeis4.)