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A053004 Decimal expansion of AGM(1,sqrt(2)). 10
1, 1, 9, 8, 1, 4, 0, 2, 3, 4, 7, 3, 5, 5, 9, 2, 2, 0, 7, 4, 3, 9, 9, 2, 2, 4, 9, 2, 2, 8, 0, 3, 2, 3, 8, 7, 8, 2, 2, 7, 2, 1, 2, 6, 6, 3, 2, 1, 5, 6, 5, 1, 5, 5, 8, 2, 6, 3, 6, 7, 4, 9, 5, 2, 9, 4, 6, 4, 0, 5, 2, 1, 4, 1, 4, 3, 9, 1, 5, 6, 7, 0, 8, 3, 5, 8, 8, 5, 5, 5, 6, 4, 8, 9, 7, 9, 3, 3, 8, 9, 3, 7, 5, 9, 0 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

AGM(a,b) is the limit of the arithmetic-geometric mean iteration applied repeatedly starting with a and b: a_0=a, b_0=b, a_{n+1}=(a_n+b_n)/2, b_{n+1}=sqrt(a_n*b_n).

REFERENCES

George Boros and Victor H. Moll, Irresistible integrals, Cambridge University Press (2006), p. 195.

J. M. Borwein and P. B. Borwein, Pi and the AGM, page 5.

J. R. Goldman, The Queen of Mathematics, 1998, p. 92.

LINKS

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

Eric Weisstein's World of Mathematics, Gauss's Constant.

Index entries for transcendental numbers

FORMULA

Equals Pi/(2*A085565). - Nathaniel Johnston, May 26 2011

Also equals Integral_{x=0..Pi/2} sqrt(sin(x)) or Integral_{x=0..1} sqrt(x/(1-x^2)). - Jean-François Alcover, Apr 29 2013 [cf. Boros & Moll p. 195]

Equals Product_{n>=1} (1+1/A033566(n)) and also 2*AGM(1, i)/(1+i)) where i is the imaginary unit. - Dimitris Valianatos, Oct 03 2016

Conjecturally equals 1/( Sum_{n = -inf..inf} exp(-Pi*(n+1/2)^2 ) )^2. Cf. A096427. - Peter Bala, Jun 10 2019

EXAMPLE

1.19814023473559220743992249228...

MATHEMATICA

RealDigits[ N[ ArithmeticGeometricMean[1, Sqrt[2]], 105]][[1]] (* Jean-François Alcover, Jan 30 2012 *)

RealDigits[N[(1+Sqrt[2])Pi/(4EllipticK[17-12Sqrt[2]]), 105]][[1]] (* Jean-François Alcover, Jun 02 2019 *)

PROG

(PARI) default(realprecision, 20080); x=agm(1, sqrt(2)); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b053004.txt", n, " ", d)) \\ Harry J. Smith, Apr 20 2009

(PARI) 2*real(agm(1, I)/(1+I)) \\ Michel Marcus, Jul 26 2018

(Python)

from mpmath import *

mp.dps=106

print map(int, list(str(agm(1, sqrt(2))).replace('.', '')[:-1])) # Indranil Ghosh, Jul 11 2017

CROSSREFS

Cf. A014549, A053002, A053003, A096427.

Sequence in context: A261813 A198920 A244115 * A019888 A154975 A199472

Adjacent sequences:  A053001 A053002 A053003 * A053005 A053006 A053007

KEYWORD

nonn,cons,nice,easy

AUTHOR

N. J. A. Sloane, Feb 21 2000

EXTENSIONS

More terms from James A. Sellers, Feb 22 2000

STATUS

approved

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Last modified July 24 04:08 EDT 2019. Contains 325290 sequences. (Running on oeis4.)