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A071946
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Triangle T(n,k) read by rows giving number of underdiagonal lattice paths from (0,0) to (n,k) using only steps R = (1,0), V = (0,1) and D = (3,1).
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5
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1, 1, 1, 1, 2, 2, 1, 4, 6, 6, 1, 6, 13, 19, 19, 1, 8, 23, 44, 63, 63, 1, 10, 37, 87, 156, 219, 219, 1, 12, 55, 155, 330, 568, 787, 787, 1, 14, 77, 255, 629, 1260, 2110, 2897, 2897, 1, 16, 103, 395, 1111, 2527, 4856, 7972, 10869, 10869, 1, 18, 133, 583, 1849, 4706, 10130, 18889, 30545, 41414, 41414
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OFFSET
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0,5
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LINKS
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EXAMPLE
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Triangle T(n,k) begins:
1;
1, 1;
1, 2, 2;
1, 4, 6, 6;
1, 6, 13, 19, 19;
...
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MAPLE
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T:= proc(n, k) option remember; `if`(n=0 and k=0, 1,
`if`(k<0 or n<k, 0, T(n-1, k)+T(n, k-1)+T(n-3, k-1)))
end:
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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