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A202062
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Number of ascent sequences avoiding the pattern 201.
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6
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1, 1, 2, 5, 15, 52, 201, 843, 3764, 17659, 86245, 435492, 2261769, 12033165, 65369590, 361661809, 2033429427, 11597912588, 67004252081, 391599609911, 2312726369640, 13789161819383, 82932744795049, 502777950712812, 3070529443569777, 18879637374473465, 116815588935673706, 727011479685559453
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OFFSET
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0,3
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COMMENTS
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It appears that no formula or g.f. is known.
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LINKS
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FORMULA
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Guttmann and Kotesovec give asymptotics: a(n) ~ c * d^n / n^(9/2), where d = (14/3*cos(arccos(13/14)/3) + 8/3) = 7.2958969432397723745722241... is the root of the equation 1 + 5*d - 8*d^2 + d^3 = 0 and c = 35*sqrt((4107 - 84*sqrt(9289) * cos(Pi/3 + arccos(255709*sqrt(9289)/24653006)/3))/Pi)/16 = 13.4299960869439... - Vaclav Kotesovec, Sep 22 2021
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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