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A090488 Decimal expansion of 2 + 2*sqrt(2). 19
4, 8, 2, 8, 4, 2, 7, 1, 2, 4, 7, 4, 6, 1, 9, 0, 0, 9, 7, 6, 0, 3, 3, 7, 7, 4, 4, 8, 4, 1, 9, 3, 9, 6, 1, 5, 7, 1, 3, 9, 3, 4, 3, 7, 5, 0, 7, 5, 3, 8, 9, 6, 1, 4, 6, 3, 5, 3, 3, 5, 9, 4, 7, 5, 9, 8, 1, 4, 6, 4, 9, 5, 6, 9, 2, 4, 2, 1, 4, 0, 7, 7, 7, 0, 0, 7, 7, 5, 0, 6, 8, 6, 5, 5, 2, 8, 3, 1, 4, 5, 4 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Side length of smallest square containing five circles of radius 1. - Charles R Greathouse IV, Apr 05 2011

Equals n + n/(n +n/(n +n/(n +....))) for n = 4.  See also A090388. - Stanislav Sykora, Jan 23 2014

Also the area of a regular octagon with unit edge length. - Stanislav Sykora, Apr 12 2015

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

Wikipedia, Octagon

Wikipedia, Regular polygon

FORMULA

Equals 1 + A086178 = 2*A014176. - R. J. Mathar, Sep 03 2007

EXAMPLE

4.828427124746190097603377448419396157139343750...

MATHEMATICA

RealDigits[2+2Sqrt[2], 10, 120][[1]] (* Harvey P. Dale, Mar 11 2015 *)

PROG

(PARI) 2*(1 + sqrt(2)) \\ G. C. Greubel, Jul 03 2017

CROSSREFS

Cf. n+n/(n+n/(n+...)): A090388 (n=2), A090458 (n=3), A090550 (n=5), A092294 (n=6), A092290 (n=7), A090654 (n=8), A090655 (n=9), A090656 (n=10). - Stanislav Sykora, Jan 23 2014

Cf. A002193, A014176, A086178.

Cf. Areas of other regular polygons: A120011, A102771, A104956, A178817, A256853, A178816, A256854, A178809.

Sequence in context: A200382 A143530 A224536 * A020848 A133058 A011516

Adjacent sequences:  A090485 A090486 A090487 * A090489 A090490 A090491

KEYWORD

easy,nonn,cons

AUTHOR

Felix Tubiana (fat2(AT)columbia.edu), Feb 05 2004

EXTENSIONS

Better definition from Rick L. Shepherd, Jul 02 2004

STATUS

approved

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Last modified February 27 13:18 EST 2020. Contains 332306 sequences. (Running on oeis4.)