A098087 Numerators of coefficients in expansion of x^2*(1-exp(-2*x))^(-2).

1, 1, 5, 1, 1, -1, -1, 1, 1, -1, -1, 1, 691, -691, -1, 2, 3617, -3617, -43867, 43867, 174611, -174611, -77683, 155366, 236364091, -236364091, -657931, 1315862, 3392780147, -6785560294, -3446336510402, 6892673020804, 7709321041217, -7709321041217, -151628697551, 151628697551

Offset: 0

Author

N. J. A. Sloane, Apr 17 2005

Keywords

• sign
• frac

Comments

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.

Crossrefs

Cf. A104007, A104042, A104097.