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A274376
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Number of modified skew Dyck paths such that the area between the x-axis and the path is n.
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1
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1, 1, 1, 1, 2, 3, 5, 8, 12, 20, 32, 52, 84, 135, 219, 353, 572, 924, 1495, 2419, 3912, 6331, 10240, 16570, 26807, 43374, 70178, 113546, 183721, 297258, 480974, 778220, 1259184, 2037389, 3296554, 5333923, 8630446, 13964340, 22594740, 36559034, 59153708, 95712668
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OFFSET
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0,5
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COMMENTS
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A modified skew Dyck path is a path in the first quadrant which begins at the origin, ends on the x-axis, consists of steps U=(1,1) (up), D=(1,-1) (down) and A=(-1,1) (anti-down) so that A and D steps do not overlap.
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LINKS
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FORMULA
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EXAMPLE
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/\ /\
a(5) = 3: /\/ \ / \/\ /\/\/\/\/\ .
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/\
\ \ /\ /\ /\
a(6) = 5: / \ / \/\/\ /\/ \/\ /\/\/ \ /\/\/\/\/\/\ .
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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