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A212209
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Square array A(n,k), n>=1, k>=1, read by antidiagonals: A(n,k) is the number of n-colorings of the square diagonal grid graph DG_(k,k).
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19
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1, 0, 2, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0, 24, 5, 0, 0, 0, 72, 120, 6, 0, 0, 0, 168, 6720, 360, 7, 0, 0, 0, 360, 935040, 126360, 840, 8, 0, 0, 0, 744, 325061760, 265035240, 1128960, 1680, 9, 0, 0, 0, 1512, 283192323840, 3322711053720, 17160407040, 6510000, 3024, 10
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OFFSET
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1,3
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COMMENTS
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The square diagonal grid graph DG_(n,n) has n^2 = A000290(n) vertices and 2*(n-1)*(2*n-1) = A002943(n-1) edges; see A212208 for example. The chromatic polynomial of DG_(n,n) has n^2+1 = A002522(n) coefficients.
This graph is also called the king graph. - Andrew Howroyd, Jun 25 2017
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LINKS
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EXAMPLE
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Square array A(n,k) begins:
1, 0, 0, 0, 0, ...
2, 0, 0, 0, 0, ...
3, 0, 0, 0, 0, ...
4, 24, 72, 168, 360, ...
5, 120, 6720, 935040, 325061760, ...
6, 360, 126360, 265035240, 3322711053720, ...
7, 840, 1128960, 17160407040, 2949948395735040, ...
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CROSSREFS
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Rows n=1-16 give: A000007, A000038, 3*A000007, 4*A068293, 5*A068294, 6*A068295, 7*A068296, 8*A068297, 9*A068298, 10*A068299, 11*A068300, 12*A068301, 13*A068302, 14*A068303, 15*A068304, 16*A068305.
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KEYWORD
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AUTHOR
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STATUS
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approved
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