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A109577
E.g.f.: 2x/[1-exp(-2x)+2exp(-x)].
0
0, 1, 0, 3, -12, 65, -450, 3577, -32424, 331137, -3757350, 46892681, -638447436, 9416929249, -149581289130, 2545707159465, -46213451575248, 891368532889601, -18204123410896590, 392431030262264329, -8904987308885931060, 212174197452256551393, -5296088301994320448530
OFFSET
0,4
FORMULA
E.g.f.: (2*x)/(1-exp(-2*x)+2*exp(-x))=2*x/(1 +2*G(0)) ; G(k)= 1-(2^k)/(2-4*x/(2*x+(2^k)*(k+1)/G(k+1))); (continued fraction Euler's kind, 1-step ). - Sergei N. Gladkovskii, Jan 08 2012
a(n) ~ n! * (-1)^(n+1) * (1-1/sqrt(2))/log(1+sqrt(2))^n. - Vaclav Kotesovec, Sep 26 2013
MAPLE
G:=2*x/(1-exp(-2*x)+2*exp(-x)): Gser:=series(G, x=0, 26): 0, seq(n!*coeff(Gser, x^n), n=1..23); # yields the signed sequence
MATHEMATICA
g[x_] = x/(-1 + Exp[ -2*x] - 2*Exp[ -x]) h[x_, n_] = Dt[g[x], {x, n}] a[x_] = Table[h[x, n], {n, 0, 50}]; b = 2*a[0]
CROSSREFS
Sequence in context: A216373 A200309 A256124 * A368265 A242575 A144297
KEYWORD
sign
AUTHOR
Roger L. Bagula, Jun 28 2005
STATUS
approved