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A180014
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Decimal expansion of Pi/(2*phi^2).
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1
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5, 9, 9, 9, 9, 0, 8, 0, 7, 4, 3, 2, 1, 6, 3, 3, 3, 0, 5, 5, 7, 8, 8, 8, 8, 7, 6, 6, 5, 8, 4, 0, 3, 4, 6, 3, 2, 8, 1, 2, 4, 9, 7, 5, 2, 7, 6, 4, 5, 2, 8, 7, 6, 0, 7, 3, 3, 7, 7, 8, 1, 8, 7, 6, 8, 2, 8, 2, 6, 8, 3, 4, 5, 5, 9, 8, 5, 9, 6, 9, 7, 6, 9, 4, 9, 9, 0, 5, 1, 5, 1, 6, 5, 1, 4, 5, 9, 9, 0, 9, 3, 2, 8, 4, 3, 2, 4, 0, 6
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OFFSET
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0,1
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COMMENTS
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This is the first of the three angles (in radians) of a unique triangle that is right angled and where the angles are in a Geometric Progression - pi/(2*phi^2), pi/(2*phi), pi/2. The angles (in degrees) are approx 34.377, 55.623, 90.
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LINKS
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Table of n, a(n) for n=0..108.
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FORMULA
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pi/(2*phi^2) = A019669 / A104457 = (3 - sqrt(5)) * Pi/4.
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EXAMPLE
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0.5999908074321633305578888766584034632812497527645287607337781876828268345598596...
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MATHEMATICA
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RealDigits[N[Pi/(2(GoldenRatio)^2), 100]][[1]]
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PROG
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(PARI) Pi/4*(3-sqrt(5)) \\ Charles R Greathouse IV, Jul 29 2011
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CROSSREFS
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Sequence in context: A086731 A147776 A020846 * A105643 A175373 A175363
Adjacent sequences: A180011 A180012 A180013 * A180015 A180016 A180017
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KEYWORD
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easy,nonn,cons,changed
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AUTHOR
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Frank M Jackson, Aug 06 2010
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EXTENSIONS
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Partially edited by R. J. Mathar, Aug 07 2010
Mathematica program edited by Harvey P. Dale, Jul 10 2012
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STATUS
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approved
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