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A003127
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Value of an urn with n balls of type -1 and n balls of type +1.
(Formerly M3537)
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0
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0, 1, 4, 17, 70, 282, 1136, 4583, 18457, 74131, 296945, 1190344, 4773949, 19145523, 76751393, 307503585, 1231182078, 4929075135, 19736248104, 79031964989, 316476142454, 1267191674419, 5073155081395, 20306187559891, 81265371486027
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OFFSET
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1,3
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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MATHEMATICA
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w[a_, 0] = a; w[0, b_] = 0; w[a_, b_] := w[a, b] = Max[ (a(1 + w[a-1, b]) + b(-1 + w[a, b-1])) / (a+b), 0]; Table[w[n, n] * Binomial[2n, n], {n, 0, 40}] (* Joel B. Lewis, Aug 27 2009 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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