cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Previous Showing 11-13 of 13 results.

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

Original entry on oeis.org

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

Views

Author

Vladimir Joseph Stephan Orlovsky, Jun 16 2010

Keywords

Examples

			2.07652139657233656716353886148584033070572020662596852408341737686302...

Links

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

A374957 Decimal expansion of the circumradius of a regular heptagon with unit side length.

Original entry on oeis.org

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

Views

Author

Paolo Xausa, Jul 26 2024

Keywords

Examples

			1.15238243548124325262057511177342755672225094380...

Links

Crossrefs

Cf. A374971 (apothem), A374972 (sagitta), A178817 (area).
Cf. circumradius of other polygons with unit side length: A020760 (triangle), A010503 (square), A300074 (pentagon), A285871 (octagon), A375151 (9-gon), A001622 (10-gon), A375190 (11-gon), A188887 (12-gon).
Cf. A073052, A121598, A272487.

Programs

Formula

Equals csc(Pi/7)/2 = A121598/2.
Equals 1/(2*sin(Pi/7)) = 1/A272487.
Equals A374971/cos(Pi/7) = A374971/A073052.
Largest of the 6 real-valued roots of 7*x^6-14*x^4+7*x^2-1=0. - R. J. Mathar, Aug 29 2025

A216606 Decimal expansion of 360/7.

Original entry on oeis.org

5, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7
Offset: 2

Views

Author

Paul Curtz, Sep 10 2012

Keywords

Comments

A020806 preceded by a 5.
Number of degrees in the exterior angle of an equilateral heptagon. Since 1969, used in many (orbiform or Reuleaux) heptagonal coins. Zambia has a natural heptagonal coin. Brazil and Costa Rica have a coin with the natural heptagon inscribed in the coin's disk.

Examples

			51.42857...

Links

Crossrefs

Cf. A019695, A020806, A021018, A060708, A068028, A178817, A178818.

Programs

Formula

a(n) = 50 + 10*A020806(n).
After 5, of period 6: repeat [1, 4, 2, 8, 5, 7].
From Wesley Ivan Hurt, Jun 28 2016: (Start)
G.f.: x^3*(5-4*x+3*x^2+3*x^3+2*x^4) / (1-x+x^3-x^4).
a(n) = 9/2 + 11*cos(n*Pi)/6 + 5*cos(n*Pi/3)/3 + sqrt(3)*sin(n*Pi/3), n>2.
a(n) = a(n-1) - a(n-3) + a(n-4) for n>6, a(n) = a(n-6) for n>8. (End)
Previous Showing 11-13 of 13 results.

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