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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 along diagonals. 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, A. J. Guttmann, Exact generating function for 2-convex polygons, J. Phys A: Math. Theor. 41 (2008) 055001, eq (31). Iwan Jensen, The anisotropic GF in Maple Friendly format. 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 Adjacent sequences:  A157515 A157516 A157517 * A157519 A157520 A157521 KEYWORD nonn,tabl AUTHOR R. J. Mathar, Mar 02 2009 STATUS approved

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Last modified May 21 15:36 EDT 2022. Contains 353921 sequences. (Running on oeis4.)