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 A151817 a(n) = 2*(2*n)!/n!. 2
 2, 4, 24, 240, 3360, 60480, 1330560, 34594560, 1037836800, 35286451200, 1340885145600, 56317176115200, 2590590101299200, 129529505064960000, 6994593273507840000, 405686409863454720000, 25152557411534192640000, 1660068789161256714240000, 116204815241287969996800000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Row sums of A155951. LINKS G. C. Greubel, Table of n, a(n) for n = 0..364 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). - Alexander R. Povolotsky, Jul 06 2009 E.g.f.: 2/(1-4*x)^(1/2).- Sergei N. Gladkovskii, Dec 05 2011 G.f.: G(0), where G(k)= 1 + 1/(1 - x*(4*k+2)/(x*(4*k+2) + 1/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 04 2013 a(n) = A052718(n+1), n>0. a(n) = 2*A001813(n). - R. J. Mathar, Mar 12 2017 MATHEMATICA Table[2*(2*n)!/n!, {n, 0, 50}] (* G. C. Greubel, Feb 21 2017 *) PROG (PARI) a(n)=2*(2*n)!/n! \\ Charles R Greathouse IV, Dec 05 2011 CROSSREFS Cf. A052718. Sequence in context: A141307 A190655 A038049 * A265937 A038058 A062531 Adjacent sequences:  A151814 A151815 A151816 * A151818 A151819 A151820 KEYWORD nonn,easy AUTHOR Roger L. Bagula, Jan 31 2009 EXTENSIONS Typo in definition corrected by N. J. A. Sloane, Jul 12 2009 New name from Sergei N. Gladkovskii, Dec 05 2011 STATUS approved

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Last modified April 9 10:32 EDT 2020. Contains 333348 sequences. (Running on oeis4.)