A280633 Decimal expansion of 18*sin(Pi/18).

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

Offset

1,1

Comments

The ratio of the perimeter of a regular 9-gon (nonagon) to its diameter (largest diagonal).

Also least positive root of x^3 - 243x + 729.

Links

Table of n, a(n) for n=1..105.

Formula

18*A019819.

Example

3.125667198004746279330899281847666328006762189313248970252344806377184798...

Maple

evalf(18*sin(Pi/18), 100); # Wesley Ivan Hurt, Feb 01 2017

Mathematica

RealDigits[18*Sin[Pi/18], 10, 120][[1]] (* Harvey P. Dale, Dec 02 2018 *)

Prog

(PARI) 18*sin(Pi/18)

Crossrefs

Cf. For other n-gons: A010466 (n=4), 10*A019827 (n=5, 10), A280533 (n=7),A280585 (n=8), A280725(n=11), A280819 (n=12).

Sequence in context: A359753 A183386 A231818 * A084614 A050058 A144204

Adjacent sequences: A280630 A280631 A280632 * A280634 A280635 A280636

Keyword

nonn,cons

Author

Rick L. Shepherd, Jan 06 2017

Status

approved