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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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3
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OFFSET
| 1,4
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COMMENTS
| These counts have not been reduced to take account of the symmetries of the board.
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REFERENCES
| 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
| 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
| Cf. A134963, A136278, A136280.
Sequence in context: A004466 A062749 A004636 * A012471 A116187 A009790
Adjacent sequences: A136276 A136277 A136278 * A136280 A136281 A136282
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KEYWORD
| nonn
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AUTHOR
| D. E. Knuth, Mar 26 2008
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