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A157518 Symmetric array T(n,m) of the number of 2-convex polygons with 2n horizontal and 2m vertical steps, read by antidiagonals. 0
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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
4,1
COMMENTS
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."
LINKS
W. R. G. James, I. Jensen, and A. J. Guttmann, Exact generating function for 2-convex polygons, J. Phys A: Math. Theor. 41 (2008) 055001, eq (31).
EXAMPLE
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
CROSSREFS
Sequence in context: A174481 A306205 A106303 * A001526 A295940 A106304
KEYWORD
nonn,tabl
AUTHOR
R. J. Mathar, Mar 02 2009
STATUS
approved

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)