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 A126984 Expansion of 1/(1+2*x*c(x)), c(x) the g.f. of Catalan numbers A000108. 6
 1, -2, 2, -4, 2, -12, -12, -72, -190, -700, -2308, -8120, -28364, -100856, -360792, -1301904, -4727358, -17268636, -63405012, -233885784, -866327748, -3220976616, -12016209192, -44966763504, -168750724428, -634935132312, -2394717424552, -9051945482032 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Hankel transform is (-2)^n. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 FORMULA a(n) = Sum_{k=0..n} A039599(n,k)*(-3)^k. G.f.: 1/(2 - sqrt(1-4*x)). - G. C. Greubel, May 28 2019 MAPLE c:=(1-sqrt(1-4*x))/2/x: ser:=series(1/(1+2*x*c), x=0, 32): seq(coeff(ser, x, n), n=0..30); # Emeric Deutsch, Mar 24 2007 MATHEMATICA CoefficientList[Series[1/(2-Sqrt[1-4*x]), {x, 0, 30}], x] (* G. C. Greubel, May 28 2019 *) PROG (PARI) my(x='x+O('x^30)); Vec(1/(2-sqrt(1-4*x))) \\ G. C. Greubel, May 28 2019 (MAGMA) R:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( 1/(2-Sqrt(1-4*x)) )); // G. C. Greubel, May 28 2019 (Sage) (1/(2-sqrt(1-4*x))).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, May 28 2019 CROSSREFS Cf. A000108, A039599. Sequence in context: A010026 A059427 A137777 * A159749 A227293 A331391 Adjacent sequences:  A126981 A126982 A126983 * A126985 A126986 A126987 KEYWORD sign AUTHOR Philippe Deléham, Mar 21 2007 EXTENSIONS Corrected and extended by Emeric Deutsch, Mar 24 2007 STATUS approved

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Last modified May 9 19:07 EDT 2021. Contains 343746 sequences. (Running on oeis4.)