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A061897
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Square table by antidiagonals of number of routes of length 2k+n on the sides of a 2n-gon from a point to its opposite point.
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2
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1, 0, 2, 0, 0, 2, 0, 0, 4, 2, 0, 0, 8, 6, 2, 0, 0, 16, 18, 8, 2, 0, 0, 32, 54, 28, 10, 2, 0, 0, 64, 162, 96, 40, 12, 2, 0, 0, 128, 486, 328, 150, 54, 14, 2, 0, 0, 256, 1458, 1120, 550, 220, 70, 16, 2, 0, 0, 512, 4374, 3824, 2000, 858, 308, 88, 18, 2, 0, 0, 1024, 13122, 13056
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OFFSET
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0,3
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LINKS
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FORMULA
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T(0, 0)=1; if n>0, T(n, 0)=2; if k>1, T(n, k)=T(n, k-1)*A061896(n, 1)-T(n, k-2)*A061896(n, 2)+T(n, k-3)*A061896(n, 3)-T(n, k-4)*A061896(n, 4)+...T(n, k-[n/2])*A061896(n, [n/2]); if 0>k T(n, k)=0.
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EXAMPLE
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Rows start
1, 0, 0, 0, 0, ...
2, 0, 0, 0, 0, ...
2, 4, 8, 16, 32, ...
2, 6, 18, 54, 162, ...
2, 8, 28, 96, 328, ...
...
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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