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 A290159 Numerators of coefficients in Taylor series expansion of (1+x+x^2)^(1/2). 0
 1, 1, 3, -3, 3, 15, -57, 21, 867, -1893, 1581, 8283, -76953, 34203, 361551, -869691, 6420387, 34130067, -167946159, 79445631, 1696170093, -4239570255, 4083041217, 21859150803, -442212416121, 215805655695, 2316081934929, -5909439428697, 11656013746863, 62663656767603, -322045194694305, 160129270032933, 27589357112530467 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Denominators of the Taylor series expansion are given by A046161. The terms after the second are divisible by 3. The sequence of the absolute values is not monotonic. LINKS Table of n, a(n) for n=0..32. MAPLE a:= n-> numer(coeff(series(sqrt(1+x+x^2), x, n+3), x, n)): seq(a(n), n=0..35); # Alois P. Heinz, Jul 25 2017 MATHEMATICA Numerator[CoefficientList[Series[Sqrt[1+x+x^2], {x, 0, 32}], x]] PROG (PARI) x = 'x + O('x^40); apply(x->numerator(x), Vec((1+x+x^2)^(1/2))) \\ Michel Marcus, Jul 24 2017 CROSSREFS Cf. A046161 (denominators). Sequence in context: A110668 A367773 A176248 * A356388 A083562 A332860 Adjacent sequences: A290156 A290157 A290158 * A290160 A290161 A290162 KEYWORD sign,frac AUTHOR Bruno Zürcher, Jul 22 2017 STATUS approved

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Last modified September 16 13:56 EDT 2024. Contains 375976 sequences. (Running on oeis4.)