A246728 Decimal expansion of r_7, the 7th smallest radius < 1 for which a compact packing of the plane exists, with disks of radius 1 and r_7.

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

Offset

0,1

Links

Table of n, a(n) for n=0..100.

Steven R. Finch, Errata and Addenda to Mathematical Constants, p. 62.

Index entries for algebraic numbers, degree 3.

Formula

1st root of 8x^3 + 3x^2 - 2x - 1.

Example

0.53329641666031286760083809931809359409467606388528091693...

Mathematica

RealDigits[Root[8x^3 + 3x^2 - 2x - 1, x, 1], 10, 101] // First

Prog

(PARI) polrootsreal(8*x^3+3*x^2-2*x-1)[1] \\ Charles R Greathouse IV, Feb 11 2025

Crossrefs

Cf. A246723 (r_1), A246724 (r_2), A246725 (r_3), A246726 (r_4), A246727 (r_5), A002193 (r_6 = sqrt(2)-1), A246729 (r_8), A246730 (r_9).

Sequence in context: A094284 A080134 A057435 * A155685 A083565 A359199

Adjacent sequences: A246725 A246726 A246727 * A246729 A246730 A246731

Keyword

nonn,cons,easy

Author

Jean-François Alcover, Sep 02 2014

Status

approved