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A157327 Egyptian fraction expansion for Pi/4=atan(1/2)+atan(1/3) (Hutton 1776) 1
2, 3, -24, -81, 160, 1215, -896, -15309, 4608, 177147, -22528, -1948617, 106496, 20726199, -491520, -215233605, 2228224, 2195382771, -9961472, -22082967873, 44040192, 219667417263, -192937984, -2165293113021, 838860800 (list; graph; refs; listen; history; internal format)
OFFSET

0,1

COMMENTS

Sum_{n>=0} 1/a(n) = Pi/4

LINKS

X. Gourdon and P. Sebah, The constant Pi. The classic period

FORMULA

G.f.: 2*(1-4*x^2)/(1+4*x^2)^2+3*x*(1-9*x^2)/(1+9*x^2)^2

CROSSREFS

Cf. A157142, A155988, A058962.

Sequence in context: A061355 A160618 A057665 * A009231 A012304 A047157

Adjacent sequences:  A157324 A157325 A157326 * A157328 A157329 A157330

KEYWORD

frac,sign

AUTHOR

Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Feb 27 2009

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Last modified February 15 05:45 EST 2012. Contains 205694 sequences.