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2, 4, 24, 240, 3360, 60480, 1330560, 34594560, 1037836800, 35286451200, 1340885145600, 56317176115200, 2590590101299200, 129529505064960000, 6994593273507840000, 405686409863454720000, 25152557411534192640000, 1660068789161256714240000, 116204815241287969996800000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| Row sums of A155951.
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FORMULA
| (Possible closed form for all terms given) a(n) = 2^(2*n-1)* Pochhammer[1/2, -1 + n] = 2^(2*n-1)*(Gamma(1/2+n-1))/(Gamma(1/2)) = 2^(2*n-1)*(Gamma(n-1/2))/sqrt(pi) (Possible recurrence relation: for all terms given) a(n+1) = 2*(2*n-1)*a(n) [From Alexander R. Povolotsky (pevnev(AT)juno.com), Jul 06 2009]
E.g.f.: 2/(1-4*x)^(1/2).- Sergei N. Gladkovskii, Dec 05 2011
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PROG
| (PARI) a(n)=2*(2*n)!/n! \\ Charles R Greathouse IV, Dec 05 2011
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CROSSREFS
| Cf. A052718.
Sequence in context: A141307 A190655 A038049 * A038058 A062531 A141599
Adjacent sequences: A151814 A151815 A151816 * A151818 A151819 A151820
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KEYWORD
| nonn
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AUTHOR
| Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Jan 31 2009
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EXTENSIONS
| Typo in definition corrected by N. J. A. Sloane, Jul 12 2009
New name from Sergei N. Gladkovskii, Dec 05 2011
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