

A271620


First row (row 0) of the SpragueGrundy values of "3pile Sharing Nim".


0



0, 0, 1, 0, 0, 0, 1, 0, 3, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 12, 0, 1, 0, 0, 0, 1, 0, 2, 0, 1, 0, 0, 0, 1, 0, 3, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 4, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 2, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 3, 0, 1, 0, 0, 0, 1, 0, 3, 0, 1, 0, 0, 0, 1, 0, 2, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 2, 0, 1, 0, 0, 0, 1, 0, 2
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OFFSET

0,9


COMMENTS

a(n) is G(0,0,n) = G(0,n,n) for 3pile Sharing Nim.
If n is odd, a(n)=0. If n={4,12,16,20,28} (mod 32), a(n) is also 0.
If n=2 (mod 4), a(n)=1.
Thus all the "interesting" values are for n={0,8,24} (mod 32).
Ho conjectures that the sequence may be bounded. The highest value in the first thousand entries is a(24)=12.
Despite the simplicity of the "uninteresting" values, the "interesting" ones are provably not periodic, which means the entire sequence is not periodic.


LINKS

Table of n, a(n) for n=0..128.
Nhan Bao Ho, 3pile Sharing Nim and the linear time winning strategy, arXiv:1506.06961 [math.CO], 2015, submitted to Theoretical Computer Science D. (Note that Ho indexes everything from 1, but the equations are simpler when indexed from 0, so I have used 0 in this entry.)


FORMULA

a(n)=0 if and only if n=0 or n=2^{2i}(2j+1) for some i,j>=0. This by itself proves the aperiodicity, since even the locations of the 0's are not periodic. Note that i=0 covers the "n is odd" case, i=1 covers the "n={4,12,20,28} (mod 32)" cases, i=2 covers the "n=16 (mod 32)" case, and i>=3 all fall under "n=0 (mod 32)". Thus the values for n={8,24} (mod 32) can never be 0.
The formula also implies that the limit of the density of zeros as n goes to infinity is 1/2 + 1/8 + 1/32 + 1/128 + ... = 2/3.  Howard A. Landman, Apr 20 2016


EXAMPLE

a(0)=a(1)=0 because there are no moves from (0,0,0) or (0,0,1). a(2)=1 because there is a move from (0,0,2) to (0,1,1), which has no moves and hence is value 0.


CROSSREFS

Sequence in context: A291204 A331414 A111025 * A098018 A260073 A196306
Adjacent sequences: A271617 A271618 A271619 * A271621 A271622 A271623


KEYWORD

nonn,easy


AUTHOR

Howard A. Landman, Apr 10 2016


STATUS

approved



