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A157518
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Symmetric array T(n,m) of the number of 2-convex polygons with 2n horizontal and 2m vertical steps, read by antidiagonals.
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0
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6, 104, 104, 908, 1818, 908, 5298, 16560, 16560, 5298, 23261, 105510, 158768, 105510, 23261, 82603, 522325, 1086904, 1086904, 522325, 82603, 249245, 2125965, 5916957, 7962500, 5916957, 2125965, 249245, 661751, 7394811, 26917679
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OFFSET
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4,1
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COMMENTS
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The first rows and columns, n<4 or m<4, are all zero and omitted from the sequence. The type of analysis of the paper puts this in the OEIS category "walk."
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LINKS
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EXAMPLE
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The array starts at n=m=4 as
......6.....104.....908....5298...23261...82603..249245..661751.1585672
....104....1818...16560..105510..522325.2125965.7394811.22623747
....908...16560..158768.1086904.5916957.26917679.105571678
...5298..105510.1086904.7962500.46811313.232629941
..23261..522325.5916957.46811313.296064058
..82603.2125965.26917679.232629941
.249245.7394811.105571678
.661751.22623747
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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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