

A136278


Number of n X n Life configurations that are "still Life"s (unchanged in one step).


2



1, 2, 12, 83, 417, 3928, 127425, 4782725, 285886827, 29305144137, 5078448221965, 1689709601427846, 898792333612812818, 812773906928265250254, 1327574905899625395329686
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OFFSET

1,2


COMMENTS

These counts have not been reduced to take into account the symmetries of the board.


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.


LINKS

Table of n, a(n) for n=1..15.


EXAMPLE

The 83 still lifes for n=4 have wellknown names, explained in the book by Berlekamp et al.: 9 are blocks, 12 are snakes, 4 are tubs, 16 are boats, 8 are ships, 8 are aircraft carriers, 4 are beehives, 8 are eaters, 4 are loaves, 2 are barges, 4 are longboats, 2 are long barges, 1 is the pond and the other one is empty.


CROSSREFS

Cf. A134963, A136279, A136280.
Sequence in context: A199420 A235348 A052864 * A130464 A319326 A214765
Adjacent sequences: A136275 A136276 A136277 * A136279 A136280 A136281


KEYWORD

nonn


AUTHOR

Don Knuth, Mar 26 2008


EXTENSIONS

a(1) and a(7) corrected and a(11)(15) added by Tomas Rokicki, Oct 29 2010


STATUS

approved



