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A104957 Decimal expansion of the area of the regular 7-gon (heptagon) of circumradius = 1. 4
2, 7, 3, 6, 4, 1, 0, 1, 8, 8, 6, 3, 8, 1, 0, 4, 3, 3, 0, 4, 7, 9, 5, 5, 5, 8, 4, 3, 3, 5, 9, 2, 0, 2, 1, 2, 5, 8, 1, 3, 1, 7, 0, 8, 1, 5, 4, 8, 0, 4, 0, 6, 3, 5, 1, 4, 3, 2, 2, 2, 2, 3, 5, 3, 1, 5, 7, 8, 2, 1, 0, 6, 0, 7, 1, 8, 7, 7, 7, 5, 4, 5, 9, 5, 3, 0, 3, 8, 0, 2, 4, 1, 1, 8, 4, 6, 8, 4, 3, 7, 8, 1, 2, 9, 1 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Equivalently, the area in the complex plane of the smallest convex set containing all order-7 roots of unity.

LINKS

Table of n, a(n) for n=1..105.

Eric Weisstein et al., "Root of Unity."

Eric Weisstein's World of Mathematics, "de Moivre Number."

FORMULA

Root[ -823543 + 537824*#1^2 - 87808*#1^4 + 4096*#1^6 &, 5, 0] = 3*Sin[(2*Pi)/7] - Sin[(12*Pi)/7]/2

EXAMPLE

2.736410188638104330479555843359202125813170815480406351432222353...

MATHEMATICA

Floor[n/2]*Sin[(2*Pi)/n] - Sin[(4*Pi*Floor[n/2])/n]/2 /. n -> 7

CROSSREFS

Cf. A104954, A104955, A104956.

Sequence in context: A011049 A075639 A082737 * A329333 A083119 A246163

Adjacent sequences:  A104954 A104955 A104956 * A104958 A104959 A104960

KEYWORD

nonn,cons

AUTHOR

Joseph Biberstine (jrbibers(AT)indiana.edu), Mar 30 2005

STATUS

approved

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Last modified February 18 09:39 EST 2020. Contains 332011 sequences. (Running on oeis4.)