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A240530
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a(n) = 4*(2*n)! / (n!)^2.
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1
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4, 8, 24, 80, 280, 1008, 3696, 13728, 51480, 194480, 739024, 2821728, 10816624, 41602400, 160466400, 620470080, 2404321560, 9334424880, 36300541200, 141381055200, 551386115280, 2153031497760, 8416395854880, 32933722910400, 128990414732400
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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G.f.: 4/sqrt(1-4*x).
D-finite with recurrence: n*a(n) - 2*(2*n-1)*a(n-1) = 0 for n > 0.
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MAPLE
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MATHEMATICA
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Table[4*(2*n)!/(n!)^2, {n, 0, 40}] (* or *) CoefficientList[Series[4/Sqrt[1 - 4 x], {x, 0, 50}], x]
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PROG
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(Magma) [4*Binomial (2*n, n): n in [0..30]];
(PARI) vector(31, n, 4*binomial(2*n-2, n-1)) \\ G. C. Greubel, Dec 19 2019
(Sage) [4*binomial(2*n, n) for n in (0..30)] # G. C. Greubel, Dec 19 2019
(GAP) List([0..30], n-> 4*Binomial(2*n, n) ); # G. C. Greubel, Dec 19 2019
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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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