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A110371
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a(n)=[(n+1)(n+2)(n+3)...(2n)]/(1+2+3+...+n).
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0
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2, 4, 20, 168, 2016, 31680, 617760, 14414400, 392071680, 12189864960, 426645273600, 16606346803200, 711700577280000, 33307587016704000, 1690360041097728000, 92472637542405120000, 5425061402487767040000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n)=2(n-1)!*Catalan(n). a(n)=2*A065866(n-1). - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 05 2005
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FORMULA
| {2*(2n)!}/{(n+1)!*n}
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EXAMPLE
| a(4) = 5*6*7*8/10 = 168.
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MAPLE
| seq(2*(2*n)!/(n+1)!/n, n=1..20); (Deutsch)
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CROSSREFS
| Cf. A065866.
Sequence in context: A013329 A102087 A052573 * A120388 A061348 A127103
Adjacent sequences: A110368 A110369 A110370 * A110372 A110373 A110374
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KEYWORD
| easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 24 2005
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 05 2005
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