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A019694
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Decimal expansion of 2*Pi/5.
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16
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1, 2, 5, 6, 6, 3, 7, 0, 6, 1, 4, 3, 5, 9, 1, 7, 2, 9, 5, 3, 8, 5, 0, 5, 7, 3, 5, 3, 3, 1, 1, 8, 0, 1, 1, 5, 3, 6, 7, 8, 8, 6, 7, 7, 5, 9, 7, 5, 0, 0, 4, 2, 3, 2, 8, 3, 8, 9, 9, 7, 7, 8, 3, 6, 9, 2, 3, 1, 2, 6, 5, 6, 2, 5, 1, 4, 4, 8, 3, 5, 9, 9, 4, 5, 1, 2, 1, 3, 9, 3, 0, 1, 3, 6, 8, 4, 6, 8, 2
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OFFSET
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1,2
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COMMENTS
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Also, with proper offset, decimal expansion of the magnetic permeability of vacuum in SI units, mu_0 = 4*Pi*10^-7 N A^-2, an assigned metrological constant.
Regarding these, see A003678 for general context notes, references and links. - Stanislav Sykora, Jun 16 2012
Iff n is +/- 1, 2, 3, 4 or 6, then 2*cos(2*pi/n) is an integer. This formula plays a role in the short proof of the Crystallographic Restriction Theorem (see A217290). For n = 5, then 2*cos(2*pi/5) = 1/Golden Ratio = 0.6180339887..., associated with quasicrystals and 5-fold rotational symmetry. - Raphie Frank, Dec 21 2012
With offset 2 this is also the decimal expansion of 4Pi. Example: 12.5663706143591729538505735331180115... - Omar E. Pol, Jan 18 2013
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LINKS
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Table of n, a(n) for n=1..99.
NIST, Constants.
Nobelprize.org, The Discovery of Quasicrystals (PDF).
Wikipedia, Crystallographic Restriction Theorem.
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EXAMPLE
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Pi/25=0.12566370614359172953850573533118... [Vladimir Joseph Stephan Orlovsky, Dec 02 2009]
mu_0 = 12.566370614359172953850573533118... 10^-7 N/A^2. - Stanislav Sykora, Jun 16 2012
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MATHEMATICA
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RealDigits[ 2*Pi/5, 10, 111][[1]] (* Vladimir Joseph Stephan Orlovsky, Dec 02 2009 and modified by Robert G. Wilson v *)
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CROSSREFS
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Other assigned constants: A003678, A182999, A081799, A213610, A072915, A213611, A213612, A213613, A213614.
Sequence in context: A198231 A155947 A008294 * A113975 A035585 A159076
Adjacent sequences: A019691 A019692 A019693 * A019695 A019696 A019697
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KEYWORD
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nonn,cons
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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