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A121598 Decimal expansion of cosecant of 180/7 = 25.7142857+ degrees = csc(Pi/7). 4
2, 3, 0, 4, 7, 6, 4, 8, 7, 0, 9, 6, 2, 4, 8, 6, 5, 0, 5, 2, 4, 1, 1, 5, 0, 2, 2, 3, 5, 4, 6, 8, 5, 5, 1, 1, 3, 4, 4, 4, 5, 0, 1, 8, 8, 7, 6, 0, 6, 3, 2, 1, 1, 6, 2, 0, 6, 3, 1, 0, 6, 2, 9, 6, 4, 6, 6, 8, 5, 3, 3, 4, 2, 7, 7, 8, 4, 7, 9, 5, 9, 6, 3, 7, 9, 1, 1, 1, 4, 2, 1, 9, 7, 4, 7, 6, 1, 7, 9, 3, 6, 1, 5, 1, 5 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

1 + csc(Pi/7) is the radius of the smallest circle into which 8 unit circles can be packed ("r=3.304+ Proved by Braaksma in 1963.", according to the Friedman link, which has a diagram).

csc(Pi/7) is the distance between the center of the larger circle and the center of each unit circle that touches the larger circle.

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

E. Friedman, Erich's Packing Center: "Circles in Circles"

EXAMPLE

2.304764870962486505241150223546855...

MATHEMATICA

RealDigits[Csc[Pi/7], 10, 100][[1]] (* G. C. Greubel, Nov 02 2018 *)

PROG

(PARI) 1/sin(Pi/7)

(MAGMA) SetDefaultRealField(RealField(100)); R:= RealField(); 1/Sin(Pi(R)/7); // G. C. Greubel, Nov 02 2018

CROSSREFS

Cf. A121570.

Sequence in context: A286578 A010340 A049275 * A258818 A261275 A140326

Adjacent sequences:  A121595 A121596 A121597 * A121599 A121600 A121601

KEYWORD

cons,nonn

AUTHOR

Rick L. Shepherd, Aug 09 2006

STATUS

approved

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Last modified June 1 18:43 EDT 2020. Contains 334762 sequences. (Running on oeis4.)