A020781 Decimal expansion of 1/sqrt(24).

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

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• easy

Comments

Radius of the inscribed sphere (tangent to the faces) for a regular tetrahedron with unit edges. - Stanislav Sykora, Nov 20 2013

Examples

			1/sqrt(24) = 0.20412414523193150818310700622549094933... . - _Vladimir Joseph Stephan Orlovsky_, May 30 2010
		

References

• Jan Gullberg, Mathematics from the Birth of Numbers, W. W. Norton & Co., NY & London, 1997, §12.4 Theorems and Formulas (Solid Geometry), p. 450.

Links

• Ivan Panchenko, Table of n, a(n) for n = 0..1000
• Wikipedia, Tetrahedron.
• Index entries for algebraic numbers, degree 2.

Crossrefs

Cf. Platonic solids inradii: A020763 (octahedron), A179294 (icosahedron), A237603 (dodecahedron). - Stanislav Sykora, Feb 25 2014

Cf. A010464, A010480, A020763, A020853, A021028, A187110, A244980.

Programs

Mathematica

RealDigits[N[1/Sqrt[24],200]] (* Vladimir Joseph Stephan Orlovsky, May 30 2010 *)

Formula

Equals A010464/12. - Stefano Spezia, Jan 26 2025

Equals 1/A010480 = A020763/2 = 2*A020853 = A187110/3 = A244980/Pi. - Hugo Pfoertner, Jan 26 2025