A010476 Decimal expansion of square root of 20.

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

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• easy

Comments

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

Examples

			4.472135954999579392818347337462552470881236719223051448541794490821041....
		

Links

• Harry J. Smith, Table of n, a(n) for n = 1..20000
• Index entries for algebraic numbers, degree 2

Crossrefs

Except for offset, same as A020762.

Cf. A040015 (continued fraction). - Harry J. Smith, Jun 03 2009

Cf. A002163 (decimal expansion of square root of 5).

Programs

Mathematica

RealDigits[N[Sqrt[20], 100]][[1]] (* Vladimir Joseph Stephan Orlovsky, Feb 21 2011 *)

PARI

default(realprecision, 20080); x=sqrt(20); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b010476.txt", n, " ", d));  \\ Harry J. Smith, Jun 03 2009

Formula

sqrt(20) = 2*sqrt(5). - Alonso del Arte, Jun 26 2015

Equals Sum_{k>=0} binomial(2*k,k) * k/5^k. - Amiram Eldar, Aug 03 2020