A137218 -id:A137218 - cp's OEIS frontend

A019881 Decimal expansion of sin(2*Pi/5) (sine of 72 degrees).

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

Offset: 0

N. J. A. Sloane

Circumradius of pentagonal pyramid (Johnson solid 2) with edge 1. - Vladimir Joseph Stephan Orlovsky, Jul 19 2010
Circumscribed sphere radius for a regular icosahedron with unit edges. - Stanislav Sykora, Feb 10 2014
Side length of the particular golden rhombus with diagonals 1 and phi (A001622); area is phi/2 (A019863). Thus, also the ratio side/(shorter diagonal) for any golden rhombus. Interior angles of a golden rhombus are always A105199 and A137218. - Rick L. Shepherd, Apr 10 2017
An algebraic number of degree 4; minimal polynomial is 16x^4 - 20x^2 + 5, which has these smaller, other solutions (conjugates): -A019881 < -A019845 < A019845 (sine of 36 degrees). - Rick L. Shepherd, Apr 11 2017
This is length ratio of one half of any diagonal in the regular pentagon and the circumscribing radius. - Wolfdieter Lang, Jan 07 2018
Quartic number of denominator 2 and minimal polynomial 16x^4 - 20x^2 + 5. - Charles R Greathouse IV, May 13 2019
This gives the imaginary part of one of the members of a conjugate pair of roots of x^5 - 1, with real part (-1 + phi)/2 = A019827, where phi = A001622. A member of the other conjugte pair of roots is (-phi + sqrt(3 - phi)*i)/2 = (-A001622 + A182007*i)/2 = -A001622/2  + A019845*i. - Wolfdieter Lang, Aug 30 2022

			0.95105651629515357211643933337938214340569863412575022244730564443015317008...

Jan Gullberg, Mathematics from the Birth of Numbers, W. W. Norton & Co., NY & London, 1997, §12.4 Theorems and Formulas (Solid Geometry), p. 451.

Ivan Panchenko, Table of n, a(n) for n = 0..1000
Eric Weisstein's World of Mathematics, Golden Rhombus.
Wikipedia, Exact trigonometric constants.
Wikipedia, Platonic solid.
Wolfram Alpha, Johnson solid 2.
Index entries for algebraic numbers, degree 4.

Cf. A001622, A019827, A102208, A179290 (inverse), A179292, A179294, A179449, A179450, A179451, A179452, A179552, A179553, A182007.

Cf. Platonic solids circumradii: A010503 (octahedron), A010527 (cube), A179296 (dodecahedron), A187110 (tetrahedron). - Stanislav Sykora, Feb 10 2014

SetDefaultRealField(RealField(100)); Sqrt((5 + Sqrt(5))/8); // G. C. Greubel, Nov 02 2018

Digits:=100: evalf(sin(2*Pi/5)); # Wesley Ivan Hurt, Sep 01 2014

RealDigits[Sqrt[(5 + Sqrt[5])/8], 10, 111]  (* Robert G. Wilson v *)
RealDigits[Sin[2 Pi/5], 10, 111][[1]] (* Robert G. Wilson v, Jan 07 2018 *)

default(realprecision, 120);
real(I^(1/5)) \\ Rick L. Shepherd, Apr 10 2017

Equals sqrt((5+sqrt(5))/8) = cos(Pi/10). - Zak Seidov, Nov 18 2006
Equals 2F1(13/20,7/20;1/2;3/4) / 2. - R. J. Mathar, Oct 27 2008
Equals the real part of i^(1/5). - Stanislav Sykora, Apr 25 2012
Equals A001622*A182007/2. - Stanislav Sykora, Feb 10 2014
Equals sin(2*Pi/5) = sqrt(2 + phi)/2 = -sin(3*Pi/5), with phi = A001622  - Wolfdieter Lang, Jan 07 2018
Equals 2*A019845*A019863. - R. J. Mathar, Jan 17 2021

A105199 Decimal expansion of arctan(2).

Original entry on oeis.org

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

Offset: 1

Bryan Jacobs (bryanjj(AT)gmail.com), Apr 12 2005

arctan(2) + A073000 = Pi/2.
arctan(2) is the (minimal) central angle of a regular icosahedron, which is the platonic solid having 20 faces and 12 vertices. The (minimal) central angle is AOB, where A and B are any neighboring pair of vertices and O is the center. To evaluate AOB, it is helpful to start with 12 vertices: (0,c*t,d), (d,0,c*t), (c*t,d,0) where c=(1 or -1) and d=(1 or -1) and t is the golden ratio, (1+sqrt(5))/2. For neighboring vertices, one can select (t,1,0) and (0,t,1). - Clark Kimberling, Feb 10 2009
Lesser interior angle (in radians) of a golden rhombus; i.e., either of the angles bisected by the longer diagonal. A137218 is the greater interior angle. - Rick L. Shepherd, Apr 10 2017
The apex angle in the isosceles triangle that is the triangle with angles A, B and C in which the maximum values of sin(A) + sin(B)*sin(C) is attained. The maximum value is phi (A001622) (Rabinowitz, 2007). - Amiram Eldar, Aug 04 2022
Also <5_1> in Conway et al. (1999). - Eric W. Weisstein, Nov 06 2024

			1.107148717794090503017065460...

G. C. Greubel, Table of n, a(n) for n = 1..5000
G. Boros and V. Moll, Sums of arctangents and some formulas of Ramanujan, Scientia Ser. A Math. Sci 11 (2005) 13-24 [MR2196063] eq. (2.11). [From _R. J. Mathar_, Apr 12 2010]
J. H. Conway, C. Radin, L. and Sadun, On Angles Whose Squared Trigonometric Functions Are Rational. Discr. Computat. Geom., Vol. 22, (1999), pp. 321-332.
Stanley Rabinowitz, Problem 3297, Crux Mathematicorum, Vol. 33, No. 8 (2007), pp. 486 and 488; Solution to Problem 3297 by D. J. Smeenk, ibid., Vol. 34, No. 8 (2008), pp. 499-500.
Eric Weisstein's World of Mathematics, Dehn Invariant.
Eric Weisstein's World of Mathematics, Golden Rhombus.
Index entries for transcendental numbers

Cf. A001622, A195693, A197292, A197376.

Cf. A137218 (larger interior angle of the golden rhombus).

RealDigits[ArcTan[2], 10, 105][[1]] (* Indranil Ghosh, Apr 10 2017 *)

default(realprecision, 120);
atan(2) \\ Rick L. Shepherd, Apr 10 2017

Equals Sum_{k>=1} arctan(8k/(4k^4+5)). [Boros and Moll, from R. J. Mathar, Apr 12 2010]
Equals 2*A195693. - Rick L. Shepherd, Apr 10 2017
Equals arcsin(2/sqrt(5)) = arccos(1/sqrt(5)). - Amiram Eldar, Aug 04 2022
Equals 2 - log(5) + (Integral_{x=0..2} log(1 + x^2) dx)/2. - Vaclav Kotesovec, Oct 06 2023
Equals 3*A197292 = A197376/2. - Hugo Pfoertner, Nov 06 2024

Offset corrected by R. J. Mathar, Apr 12 2010

A137914 Decimal expansion of arccos(1/3).

Original entry on oeis.org

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

Offset: 1

Rick L. Shepherd, Feb 22 2008

Dihedral angle in radians of regular tetrahedron.
Arccos(1/3) is the central angle of a cube, made by the center and two neighboring vertices. - Clark Kimberling, Feb 10 2009
Also the complementary tetrahedral angle, Pi-A156546, and therefore related to the magic angle (Pi-2*A195696). - Stanislav Sykora, Jan 23 2014
Polar angle (or apex angle) of the cone that subtends exactly one third of the full solid angle. - Stanislav Sykora, Feb 20 2014
Also the acute angle in the rhombi and isosceles trapezoids in the trapezo-rhombic dodecahedron. - Eric W. Weisstein, Jan 09 2019
Also the angle between the tangent lines to the curves y = sin(x) at y = cos(x) at the points of intersection. - David Radcliffe, Jan 17 2023

			1.2309594173407746821349291782479873757103400093550948390555483336639923144...

G. C. Greubel, Table of n, a(n) for n = 1..10000
Steven R. Finch, Errata and Addenda to Mathematical Constants, p. 58.
Eric Weisstein's World of Mathematics, Tetrahedron.
Eric Weisstein's World of Mathematics, Dihedral Angle.
Eric Weisstein's World of Mathematics, Trapezo-Rhombic Dodecahedron.
Index entries for transcendental numbers

Cf. A137915 (same in degrees), A019670, A195695, A195696, A238238, Platonic solids dihedral angles: A156546 (octahedron), A019669 (cube), A236367 (icosahedron), A137218 (dodecahedron).

SetDefaultRealField(RealField(100)); Arccos(1/3); // G. C. Greubel, Aug 20 2018

RealDigits[ArcCos[1/3], 10, 120][[1]] (* Harvey P. Dale, Jul 06 2018 *)
RealDigits[ArcSec[3], 10, 120][[1]] (* Eric W. Weisstein, Jan 09 2019 *)

PARI
```
acos(1/3)
```

arccos(1/3) = arctan(2*sqrt(2)) = 2*arcsin(sqrt(3)/3) = arcsin(2*sqrt(2)/3).
Equals sqrt(2)*Sum_{k>=0} (-1)^k/(2^k*(2*k+1)). - Davide Rotondo, Jun 07 2025
Equals 2*A195695. - Hugo Pfoertner, Jun 07 2025

A156546 Decimal expansion of the central angle of a regular tetrahedron.

Original entry on oeis.org

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

Offset: 1

Clark Kimberling, Feb 09 2009

If O is the center of a regular tetrahedron ABCD, then the central angle AOB is this number; exact value is Pi - arccos(1/3).
The (minimal) central angle of the other four regular polyhedra are as follows:
- cube: A137914,
- octahedron: A019669,
- dodecahedron: A156547,
- icosahedron: A105199.
Dihedral angle of two adjacent faces of the octahedron. - R. J. Mathar, Mar 24 2012
Best known as "tetrahedral angle" theta (e.g., in chemistry). Its Pi complement (i.e., Pi - theta) is the dihedral angle between adjacent faces in regular tetrahedron. - Stanislav Sykora, May 31 2012
Also twice the magic angle (A195696). - Stanislav Sykora, Nov 14 2013

			Pi - arccos(1/3) = 1.910633236249018556..., or, in degrees, 109.471220634490691369245999339962435963006843100... = A247412

Wikipedia, Tetrahedron
Wikipedia, Tetrahedral molecular geometry
Index entries for transcendental numbers.

Cf. A195696, A247412.

Cf. Platonic solids dihedral angles: A137914 (tetrahedron), A019669 (cube), A236367 (icosahedron), A137218 (dodecahedron). - Stanislav Sykora, Jan 23 2014

evalf(arccos(-1/3)) ; # R. J. Mathar, Feb 18 2025

RealDigits[Pi-ArcCos[1/3],10,120][[1]] (* Harvey P. Dale, Aug 25 2011 *)

acos(-1/3) \\ Charles R Greathouse IV, Aug 30 2013

Start with vertices (1,1,1), (1,-1,-1,), (-1,1,-1), and (1,-1,1) and apply the formula for cosine of the angle between two vectors.
Equals 2* A195696. - R. J. Mathar, Mar 24 2012
Equals A000796 - A137914 = A247412 / A072097 - R. J. Mathar, Feb 18 2025

A378977 Decimal expansion of the dihedral angle, in radians, between any two adjacent faces in a triakis icosahedron.

Original entry on oeis.org

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

Offset: 1

Paolo Xausa, Dec 14 2024

The triakis icosahedron is the dual polyhedron of the truncated dodecahedron.

			2.8032178560848059621034493264877253281152659880354...

Paolo Xausa, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Triakis Icosahedron.
Wikipedia, Triakis icosahedron.

Cf. A378973 (surface area), A378974 (volume), A378975 (inradius), A378976 (midradius).
Cf. A137218 and A344075 (dihedral angles of a truncated dodecahedron).
Cf. A002163.

First[RealDigits[ArcCos[-3*(8 + 5*Sqrt[5])/61], 10, 100]] (* or *)
First[RealDigits[First[PolyhedronData["TriakisIcosahedron", "DihedralAngles"]], 10, 100]]

Equals arccos(-3*(8 + 5*sqrt(5))/61) = arccos(-3*(8 + 5*A002163)/61).

A236367 Dihedral angle in a regular icosahedron (radians).

Original entry on oeis.org

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

Offset: 1

Stanislav Sykora, Jan 23 2014

			2.41186499736282687500784672346618218880066348532739213...

Stanislav Sykora, Table of n, a(n) for n = 1..2000
Wikipedia, Platonic solid.

Cf. A001622, Platonic solids dihedral angles: A137914 (tetrahedron), A156546 (octahedron), A019669 (cube), A137218 (dodecahedron).

RealDigits[2 * ArcTan[GoldenRatio^2], 10, 120][[1]] (* Amiram Eldar, May 17 2023 *)

PARI
```
2*atan((3+sqrt(5))/2)
```

Equals 2*arctan(phi^2) = 2*arctan(A001622^2) = 2*arctan((3+sqrt(5))/2).

A195708 Decimal expansion of arccos(sqrt(2/5)) and of arcsin(sqrt(3/5)).

Original entry on oeis.org

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

Offset: 0

Clark Kimberling, Sep 23 2011

			0.886077123792...

G. C. Greubel, Table of n, a(n) for n = 0..5000
Index entries for transcendental numbers

Cf. A073000, A105199, A195701.

[Arccos(Sqrt(2/5))]; // G. C. Greubel, Nov 18 2017

r = Sqrt[1/5]; s = Sqrt[2/5];
N[ArcSin[r], 100]
RealDigits[%]  (* A073000 *)
N[ArcCos[r], 100]
RealDigits[%]  (* A105199 *)
N[ArcTan[r], 100]
RealDigits[%]  (* A188595 *)
N[ArcCos[-r], 100]
RealDigits[%]  (* A137218 *)
N[ArcSin[s], 100]
RealDigits[%]  (* A195701 *)
N[ArcCos[s], 100]
RealDigits[%]  (* A195708 *)
N[ArcTan[s], 100]
RealDigits[%]  (* A195709 *)
N[ArcCos[-s], 100]
RealDigits[%]  (* A195710 *)

acos(sqrt(2/5)) \\ G. C. Greubel, Nov 18 2017

Equals arctan(sqrt(3/2)). - Amiram Eldar, Jul 04 2023

A195709 Decimal expansion of arctan(sqrt(2/5)).

Original entry on oeis.org

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

Offset: 0

Clark Kimberling, Sep 23 2011

			arctan(sqrt(2/5)) = 0.5639426413606...

G. C. Greubel, Table of n, a(n) for n = 0..5000
Index entries for transcendental numbers

Cf. A195708.

[Arctan(Sqrt(2/5))]; // G. C. Greubel, Nov 18 2017

r = Sqrt[1/5]; s = Sqrt[2/5];
N[ArcSin[r], 100]
RealDigits[%]  (* A073000 *)
N[ArcCos[r], 100]
RealDigits[%]  (* A105199 *)
N[ArcTan[r], 100]
RealDigits[%]  (* A188595 *)
N[ArcCos[-r], 100]
RealDigits[%]  (* A137218 *)
N[ArcSin[s], 100]
RealDigits[%]  (* A195701 *)
N[ArcCos[s], 100]
RealDigits[%]  (* A195708 *)
N[ArcTan[s], 100]
RealDigits[%]  (* A195709 *)
N[ArcCos[-s], 100]
RealDigits[%]  (* A195710 *)

atan(sqrt(2/5)) \\ G. C. Greubel, Nov 18 2017

A195710 Decimal expansion of arccos(-sqrt(2/5)).

Original entry on oeis.org

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

Offset: 1

Clark Kimberling, Sep 23 2011

			arccos(-sqrt(2/5)) = 2.25551552979717...

G. C. Greubel, Table of n, a(n) for n = 1..5000
Index entries for transcendental numbers

Cf. A195708, A195701.

[Arccos(-Sqrt(2/5))]; // G. C. Greubel, Nov 18 2017

r = Sqrt[1/5]; s = Sqrt[2/5];
N[ArcSin[r], 100]
RealDigits[%]  (* A073000 *)
N[ArcCos[r], 100]
RealDigits[%]  (* A105199 *)
N[ArcTan[r], 100]
RealDigits[%]  (* A188595 *)
N[ArcCos[-r], 100]
RealDigits[%]  (* A137218 *)
N[ArcSin[s], 100]
RealDigits[%]  (* A195701 *)
N[ArcCos[s], 100]
RealDigits[%]  (* A195708 *)
N[ArcTan[s], 100]
RealDigits[%]  (* A195709 *)
N[ArcCos[-s], 100]
RealDigits[%]  (* A195710 *)
RealDigits[ArcCos[-Sqrt[(2/5)]],10,120][[1]] (* Harvey P. Dale, Apr 06 2023 *)

acos(-sqrt(2/5)) \\ G. C. Greubel, Nov 18 2017

Equals Pi - arcsin(sqrt(3/5)) = Pi - arctan(sqrt(3/2)). - Amiram Eldar, Jul 08 2023

A242723 Decimal expansion of 180*(1 - arctan(2)/Pi).

Original entry on oeis.org

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

Offset: 3

Arkadiusz Wesolowski, May 21 2014

Dihedral angle in degrees of regular dodecahedron.

			116.5650511770779893515721937204532946712042142996452210279860163152880...

Wikipedia, Dodecahedron

Cf. A137218 (same in radians).

RealDigits[180 (1 - ArcTan[2]/Pi), 10, 100, 2] (* Wesley Ivan Hurt, May 21 2014 *)

default(realprecision, 105); x=18/10*(1-atan(2)/Pi); for(n=1, 105, d=floor(x); x=(x-d)*10; print1(d, ", "));

cp's OEIS Frontend

A019881 Decimal expansion of sin(2*Pi/5) (sine of 72 degrees).

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A105199 Decimal expansion of arctan(2).

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A137914 Decimal expansion of arccos(1/3).

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A156546 Decimal expansion of the central angle of a regular tetrahedron.

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A378977 Decimal expansion of the dihedral angle, in radians, between any two adjacent faces in a triakis icosahedron.

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A236367 Dihedral angle in a regular icosahedron (radians).

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A195708 Decimal expansion of arccos(sqrt(2/5)) and of arcsin(sqrt(3/5)).

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