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A098087 Numerators of coefficients in expansion of x^2*(1-exp(-2*x))^(-2). 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

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.

LINKS

Table of n, a(n) for n=0..35.

CROSSREFS

Cf. A104007, A104042, A104097.

Sequence in context: A059592 A295554 A319099 * A257099 A291578 A165485

Adjacent sequences:  A098084 A098085 A098086 * A098088 A098089 A098090

KEYWORD

sign,frac

AUTHOR

N. J. A. Sloane, Apr 17 2005

STATUS

approved

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Last modified February 20 21:09 EST 2019. Contains 320350 sequences. (Running on oeis4.)