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 A171683 Triangle T(n,k) which contains 4*n!*2^floor((n+1)/2) times the coefficient [t^n x^k] exp(t*x)/(3 + exp(2*t)) in row n, column k. 1
 1, -1, 2, -1, -2, 2, 1, -6, -6, 4, 10, 4, -12, -8, 4, 26, 100, 20, -40, -20, 8, -154, 156, 300, 40, -60, -24, 8, -1646, -2156, 1092, 1400, 140, -168, -56, 16, 1000, -13168, -8624, 2912, 2800, 224, -224, -64, 16, 92744, 18000, -118512, -51744, 13104, 10080 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The bivariate taylor expansion of exp(t*x)/(3+exp(2*t)) is 1/4 + (x/4-1/8)*t +(-1/16+x^2/8-x/8)*t^2+... Row n contains the coefficients of [x^k] of the polynomial in front of t^n, multiplied by 4*floor[(n+1)/2]*n!. Row sums are: 1, 1, -1, -7, -2, 94, 266, -1378, -15128, -36344, 839144,... LINKS EXAMPLE The triangle starts in row n=0, columns 0<=k <=n as 1; -1, 2; -1, -2, 2; 1, -6, -6, 4; 10, 4, -12, -8, 4; 26, 100, 20, -40, -20, 8; -154, 156, 300, 40, -60, -24, 8; -1646, -2156, 1092, 1400, 140, -168, -56, 16; 1000, -13168, -8624, 2912, 2800, 224, -224, -64, 16; 92744, 18000, -118512, -51744, 13104, 10080, 672, -576, -144, 32; 302984, 927440, 90000, -395040, -129360, 26208, 16800, 960, -720, -160, 32; MATHEMATICA Clear[p, g, m, a]; m = 1; p[t_] = 2^(m + 1)*Exp[t*x]/(-1 + 2^(m + 1) + Exp[2^m*t]) Table[ FullSimplify[ExpandAll[2^ Floor[(n + 1)/2]*n!*SeriesCoefficient[ Series[p[t], {t, 0, 30}], n]]], {n, 0, 10}] a = Table[CoefficientList[FullSimplify[ExpandAll[2^Floor[(n + 1)/2]*n!*SeriesCoefficient[ Series[p[t], {t, 0, 30}], n]]], x], {n, 0, 10}] Flatten[a] CROSSREFS Cf. A000364, A060083, A171684 Sequence in context: A166548 A273138 A181281 * A249130 A134997 A355691 Adjacent sequences: A171680 A171681 A171682 * A171684 A171685 A171686 KEYWORD sign,tabl AUTHOR Roger L. Bagula, Dec 15 2009 EXTENSIONS Number of variables in use reduced from 4 to 2, keyword:tabl added - The Assoc. Eds. of the OEIS, Oct 20 2010 STATUS approved

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Last modified January 26 20:21 EST 2023. Contains 359833 sequences. (Running on oeis4.)