A179050 Decimal expansion of 5/(2*sqrt(5+2*sqrt(5))), area of regular pentagram with base edge length 1.

8, 1, 2, 2, 9, 9, 2, 4, 0, 5, 8, 2, 2, 6, 5, 8, 1, 5, 3, 8, 9, 6, 7, 8, 5, 3, 0, 5, 3, 7, 8, 3, 6, 1, 6, 2, 3, 8, 7, 2, 5, 8, 6, 7, 8, 8, 0, 3, 6, 8, 7, 7, 5, 0, 7, 6, 9, 5, 1, 1, 7, 9, 7, 8, 4, 1, 6, 8, 2, 2, 5, 2, 4, 0, 1, 8, 6, 2, 3, 7, 0, 8, 0, 6, 7, 1, 9, 3, 3, 8, 6, 1, 7, 4, 1, 2, 6, 2, 6, 2, 0, 4, 2, 5, 9

Offset

0,1

Comments

An algebraic number of degree 4: the smaller positive root of 16x^4 - 200x^2 + 125. - Charles R Greathouse IV, Dec 03 2012

Links

Table of n, a(n) for n=0..104.

Thomas M. Green, Area of Pentagram

Index entries for algebraic numbers, degree 4

Example

0.81229924058226581538967853053783616238725867880368775076951179784168...

Mathematica

a=1; area=5/(2*Sqrt[5+2*Sqrt[5]]); RealDigits[N[area, 20]]

Prog

(PARI) 5/sqrt(20+8*sqrt(5)) \\ Charles R Greathouse IV, Dec 03 2012

Crossrefs

Cf. A002194, A010502, A102771, A120011, A179047, A179048, A104956.

Sequence in context: A225767 A019763 A307506 * A176458 A355708 A222217

Adjacent sequences: A179047 A179048 A179049 * A179051 A179052 A179053

Keyword

nonn,cons,easy

Author

Vladimir Joseph Stephan Orlovsky, Jun 26 2010

Extensions

Offset corrected, keyword:cons inserted by R. J. Mathar, Jun 28 2010

Name corrected by Charles R Greathouse IV, Dec 03 2012

Status

approved