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4, 32, 512, 12288, 393216, 15728640, 754974720, 42278584320, 2705829396480, 194819716546560, 15585577323724800, 1371530804487782400, 131666957230827110400, 13693363552006019481600
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internal format)
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OFFSET
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0,1
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COMMENTS
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A binomial sequence that produces Pi: 1/Pi= Binomial[2*n+1,n+1/2]/(2*n+1)!!
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LINKS
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FORMULA
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E.g.f.: 4/(1 - 8*x).
a(n) ~ sqrt(Pi)*2^(3*n+5/2)*n^(n+1/2)/exp(n). (End)
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MATHEMATICA
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Table[(2*n + 1)!!*Pi*Gamma[2*n + 2]/(Gamma[n + 3/2]^2), {n, 0, 20}]
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PROG
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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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