A010474 - OEIS

A010474

Decimal expansion of square root of 18.

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

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OFFSET

1,1

COMMENTS

Continued fraction expansion is 4 followed by {4, 8} repeated. - Harry J. Smith, Jun 05 2009

3*sqrt(2) = sqrt(18) is also the minimum width of the arms of the cellular automaton described in A294020. - Omar E. Pol, Oct 29 2017

Equals lambda(3) where lambda(n) = n*Product_{k=2..n-1} k^((n-k)/(n-k+1)). - Michel Marcus, Apr 02 2020

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..20000

Michael Penn, A nice algebra problem with complex numbers, YouTube video, 2022.

Index entries for algebraic numbers, degree 2

EXAMPLE

4.242640687119285146405066172629094235709015626130844219530039213972197....

MAPLE

evalf[100](sqrt(18)); # Muniru A Asiru, Feb 12 2019

MATHEMATICA

RealDigits[Sqrt[18], 10, 100][[1]] (* Vladimir Joseph Stephan Orlovsky, Feb 21 2011 *)

PROG

(PARI) default(realprecision, 100); sqrt(18) \\ Harry J. Smith, Jun 03 2009 (modified by G. C. Greubel, Feb 14 2019)

(Magma) SetDefaultRealField(RealField(100)); Sqrt(18); // G. C. Greubel, Feb 14 2019

(Sage) numerical_approx(sqrt(18), digits=100) # G. C. Greubel, Feb 14 2019

CROSSREFS

Cf. A040013 (continued fraction). - Harry J. Smith, Jun 03 2009

Sequence in context: A300004 A147973 A278527 * A064887 A114424 A246819

Adjacent sequences: A010471 A010472 A010473 * A010475 A010476 A010477

KEYWORD

nonn,cons

AUTHOR

N. J. A. Sloane

STATUS

approved