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 A126985 Expansion of 1/(1+8*x*c(x)), c(x) the g.f. of Catalan numbers A000108. 6
 1, -8, 56, -400, 2840, -20208, 143664, -1021728, 7265240, -51665200, 367392656, -2612584928, 18578329456, -132112749920, 939467783520, -6680662171200, 47506922377560, -337827035002800, 2402325467002320, -17083203745473120, 121480558396908240, -863861754435010080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Hankel transform is (-8)^n. Catalan transform of (-1)^n*A001018(n). - R. J. Mathar, Nov 11 2008 LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 FORMULA a(n) = Sum_{k=0..n} A039599(n,k)*(-9)^k. G.f.: 2/(10 - 8*sqrt(1-4*x)). - G. C. Greubel, May 28 2019 MAPLE c:=(1-sqrt(1-4*x))/2/x: ser:=series(1/(1+8*x*c), x=0, 25): seq(coeff(ser, x, n), n=0..21); # Emeric Deutsch, Mar 24 2007 MATHEMATICA CoefficientList[Series[2/(10-8*Sqrt[1-4*x]), {x, 0, 30}], x] (* G. C. Greubel, May 28 2019 *) PROG (PARI) my(x='x+O('x^30)); Vec(2/(10-8*sqrt(1-4*x))) \\ G. C. Greubel, May 28 2019 (MAGMA) R:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( 2/(10-8*Sqrt(1-4*x)) )); // G. C. Greubel, May 28 2019 (Sage) (2/(10-8*sqrt(1-4*x))).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, May 28 2019 CROSSREFS Cf. A000108, A001018, A039599. Sequence in context: A003950 A252701 A033134 * A323699 A323700 A182430 Adjacent sequences:  A126982 A126983 A126984 * A126986 A126987 A126988 KEYWORD sign AUTHOR Philippe Deléham, Mar 21 2007 EXTENSIONS More terms from Emeric Deutsch, Mar 24 2007 STATUS approved

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Last modified October 15 00:14 EDT 2019. Contains 328025 sequences. (Running on oeis4.)