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Search: id:A136279
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| A136279 |
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Number of n X n Life configurations that are "flip-flops" (Life cycles of period 2). |
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+0
4
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OFFSET
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1,4
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COMMENT
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These counts have not been reduced to take account of the symmetries of the board.
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REFERENCES
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E. R. Berlekamp, J. H. Conway and R. K. Guy, Winning Ways, Academic Press, NY, 2 vols., 1982; see Chapter 25.
D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.4.
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EXAMPLE
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The 12 solutions for n=4 belong to four isomorphism classes under symmetry:
The blinker, four cases:
..State 1. ..State 2.
.......... ....*.....
...***.... ....*.....
.......... ....*.....
.......... ..........
The toad, four cases:
..State 1. ..State 2.
.....*.... ..........
...*..*... ....***...
...*..*... ...***....
....*..... ..........
The beacon, two cases:
..State 1. ..State 2.
.....**... .....**...
......*... .....**...
...*...... ...**.....
...**..... ...**.....
The clock, two cases:
..State 1. ..State 2.
.....*.... ....*.....
...*.*.... .....**...
....*.*... ...**.....
....*..... .....*....
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CROSSREFS
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Cf. A134963, A136278, A136280.
Adjacent sequences: A136276 A136277 A136278 this_sequence A136280 A136281 A136282
Sequence in context: A004466 A062749 A004636 this_sequence A012471 A116187 A009790
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KEYWORD
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nonn
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AUTHOR
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D. E. Knuth, Mar 26 2008
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