A010477 Decimal expansion of square root of 21.

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

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy
• cons

Comments

Continued fraction expansion is 4 followed by {1, 1, 2, 1, 1, 8} repeated. - Harry J. Smith, Jun 03 2009

The fundamntal algebraic (integer) number in the field Q(sqrt(21)) is (1 + sqrt(21))/2 = A222134. - Wolfdieter Lang, Nov 21 2023

Examples

			4.582575694955840006588047193728008488984456576767971902607242123906868...
		

Links

• Harry J. Smith, Table of n, a(n) for n = 1..20000
• Frankfurter Allgemeine Zeitung, Feb 09 2011 (in German)
• Index entries for algebraic numbers, degree 2

Crossrefs

Cf. A010125 (continued fraction), A248249 (Egyptian fraction).

Cf. A020778 (reciprocal), A222134.

Programs

Mathematica

RealDigits[N[Sqrt[21],200]][[1]] (* Vladimir Joseph Stephan Orlovsky, Feb 22 2011 *)

PARI

default(realprecision, 20080); x=sqrt(21); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b010477.txt", n, " ", d));  \\ Harry J. Smith, Jun 03 2009