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A280777
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Denominators of coefficients in asymptotic expansion of C_n (number of connected chord diagrams, A000699).
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6
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1, 2, 8, 16, 128, 1280, 3072, 215040, 3440640, 2293760, 137625600, 201850880, 72666316800, 1889324236800, 52901078630400, 176336928768000, 135426761293824, 191854578499584000, 1593868805996544000, 787371190162292736000, 31494847606491709440000, 29395191099392262144000
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OFFSET
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0,2
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LINKS
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EXAMPLE
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Coefficients are 1, -5/2, -43/8, -579/16, -44477/128, -5326191/1280, -180306541/3072, ...
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PROG
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(PARI)
my(a = vector(N)); a[1] = 1;
for (n=2, N, a[n] = sum(k=1, n-1, (2*k-1)*a[k]*a[n-k])); a;
};
seq(N) = my(C = 'x*Ser(A000699_seq(N))); Vec(x*exp(1-(2*C+C^2)/(2*x))/C);
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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