A391655 Decimal expansion of the circumradius of a Dürer's solid with unit shorter edge length.

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

Offset

1,1

Comments

The value of this constant is based on the interpretation of Dürer's solid given in A391653. See there for more information and links.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Formula

Equals sqrt((17 + 7*sqrt(5))/8) = sqrt((17 + 7*A002163)/8).

Equals the largest root of 16*x^4 - 68*x^2 + 11.

Example

2.020286979691824867441123401144768438405308621338...

Mathematica

First[RealDigits[Sqrt[(17 + 7*Sqrt[5])/8], 10, 100]] (* or *)
First[RealDigits[PolyhedronData["DuererSolid", "Circumradius"], 10, 100]]

Crossrefs

Cf. A391653 (volume), A391654 (surface area).

Cf. dihedral angles: A238238, A391656, A391657.

Cf. A080992, A002163.

Sequence in context: A291968 A226171 A284280 * A278520 A239246 A171700

Adjacent sequences: A391652 A391653 A391654 * A391656 A391657 A391658

Keyword

nonn,cons,easy

Author

Paolo Xausa, Dec 15 2025

Status

approved