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Numerators of coefficients in expansion of x^2*(1-exp(-2*x))^(-2).
3

%I #5 Mar 30 2012 16:50:02

%S 1,1,5,1,1,-1,-1,1,1,-1,-1,1,691,-691,-1,2,3617,-3617,-43867,43867,

%T 174611,-174611,-77683,155366,236364091,-236364091,-657931,1315862,

%U 3392780147,-6785560294,-3446336510402,6892673020804,7709321041217,-7709321041217,-151628697551,151628697551

%N Numerators of coefficients in expansion of x^2*(1-exp(-2*x))^(-2).

%C Suggested by Bill Gosper's remarkable identity (in a posting to math-fun list, Apr 14 2005) (replace dots by spaces to make this more visible): Product_{ n >= 0 } tanh(2^n x)^(1/2^n) = (1-exp(-2*x))^2.

%Y Cf. A104007, A104042, A104097.

%K sign,frac

%O 0,3

%A _N. J. A. Sloane_, Apr 17 2005