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A121299
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Sum of the heights of all directed column-convex polyominoes of area n; here by the height of a polyomino one means the number of lines of slope -1 that pass through the centers of the polyomino cells.
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2
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1, 4, 14, 47, 149, 458, 1373, 4046, 11765, 33857, 96611, 273760, 771164, 2161352, 6031104, 16764719, 46442640, 128268379, 353296944, 970717966, 2661204271, 7280832780, 19882745230, 54203791062, 147536291969, 400991600305
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(2)=4 because the vertical and the horizontal dominoes have altogether 4 diagonals with slope -1.
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MAPLE
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T:=proc(n, k) if n<=0 or k<=0 then 0 elif n=1 and k=1 then 1 else T(n-1, k-1)+add(T(n-k, j), j=1..k-1)+add(T(n-j, k-1), j=1..k-1) fi end: seq(add(k*T(n, k), k=1..n), n=1..15);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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