A178818 Decimal expansion of the diameter of the regular 7-gon (heptagon) of edge length 1.

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

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Jun 16 2010

Keywords

• nonn
• easy
• cons
• changed

Examples

			2.07652139657233656716353886148584033070572020662596852408341737686302...
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000
• Index entries for algebraic numbers, degree 6.

Crossrefs

Cf. A090488, A102771, A104956, A120011, A178809, A178816, A178817.

Programs

Magma

SetDefaultRealField(RealField(100)); R:=RealField(); Cot(Pi(R)/7); // G. C. Greubel, Jan 22 2019

Maple

evalf[120](cot(Pi/7)); # Muniru A Asiru, Jan 22 2019

Mathematica

RealDigits[Cot[Pi/7],10, 100][[1]]

PARI

default(realprecision, 100); cotan(Pi/7) \\ G. C. Greubel, Jan 22 2019

Sage

numerical_approx(cot(pi/7), digits=100) # G. C. Greubel, Jan 22 2019

Formula

Digits of cot(Pi/7).

Largest of the 6 real-valued roots of 7*x^6 -35*x^4 +21*x^2 -1=0. - R. J. Mathar, Aug 29 2025