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

1,1

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

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

Example

4.582575694955840006588047193728008488984456576767971902607242123906868...

Mathematica

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

Prog

(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

Crossrefs

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

Cf. A020778 (reciprocal), A222134.

Sequence in context: A152974 A180307 A263208 * A195386 A259468 A143717

Adjacent sequences: A010474 A010475 A010476 * A010478 A010479 A010480

Keyword

nonn,easy,cons

Author

N. J. A. Sloane

Status

approved