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A000163
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Series-parallel numbers.
(Formerly M1852 N0732)
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1
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2, 8, 34, 136, 538, 2080, 7970, 30224, 113874, 426520, 1590338, 5906640, 21866794, 80725280, 297292610, 1092539736, 4007553922, 14675748416, 53663197698, 195962433328, 714734393378, 2603994002280, 9477643739746, 34463730424720
(list;
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listen;
history;
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OFFSET
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2,1
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REFERENCES
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J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 142.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
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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n = 25; s = 1/(1 - x) + O[x]^(n + 1); Do[s = s/(1 - x^k)^Coefficient[s, x^k] + O[x]^(n + 1), {k, 2, n}] ; S = s - 1; CoefficientList[2*(1 + S)/(1 - S)^3 + O[x]^n, x] (* Jean-François Alcover, Feb 09 2016 *)
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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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