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 A106193 Expansion of sqrt(1-4x)/(1-2x^2). 0
 1, -2, 0, -8, -10, -44, -104, -352, -1066, -3564, -11856, -40720, -141284, -497464, -1768368, -6343808, -22926426, -83402956, -305142432, -1122083312, -4144811244, -15372407464, -57222156528, -213709942208, -800563540356, -3007228179064, -11325019883616 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n)=sum{k=0..floor(n/2), binomial(2(n-2k), n-2k)/(1-2(n-2k))*2^k}. Conjecture: n*a(n) +2*(-2*n+3)*a(n-1) -2*n*a(n-2) +4*(2*n-3)*a(n-3)=0. - R. J. Mathar, Feb 20 2015 MATHEMATICA CoefficientList[Series[Sqrt[1-4x]/(1-2x^2), {x, 0, 30}], x] (* Harvey P. Dale, Mar 31 2015 *) CROSSREFS Cf. A106192. Sequence in context: A097348 A271034 A185965 * A085814 A009524 A009794 Adjacent sequences:  A106190 A106191 A106192 * A106194 A106195 A106196 KEYWORD easy,sign AUTHOR Paul Barry, Apr 24 2005 STATUS approved

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