A179552 Decimal expansion of the volume of pentagonal pyramid with edge length 1.

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

Offset: 0

Author

Vladimir Joseph Stephan Orlovsky, Jul 19 2010

Keywords

• nonn
• cons
• easy

Comments

Pentagonal pyramid: 6 faces, 6 vertices, and 10 edges.

Also equals the covariance-matrix eigenvalue of the regular icosahedron with unit edge lengths. - Chittaranjan Pardeshi, Jul 18 2025

Examples

			0.3015028323958245706837155695304698431433590983171469051779540518921...
		

Links

• Wikipedia, Covariance matrix.
• Wikipedia, Regular icosahedron.
• Wolfram Alpha, Johnson solid 2
• Index entries for algebraic numbers, degree 2

Crossrefs

Cf. A001622, A010527, A102208, A179290, A179292, A179294, A179449, A179450, A179451, A179452.

Programs

Mathematica

RealDigits[N[(5+Sqrt[5])/24,200]]

PARI

(5+sqrt(5))/24 \\ Charles R Greathouse IV, Oct 30 2023

Formula

Equals (5+sqrt(5))/24.