OFFSET
1,1
COMMENTS
Appears as constant factor in Proposition 1.12, p. 5, of Feige et al. (2007). - Jonathan Vos Post, Jun 18 2007
REFERENCES
C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Oxford University Press, Oxford and NY, 2001, page 68.
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..20000
C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Zentralblatt review
Uri Feige, Guy Kindler, Ryan O Donnell, Understanding Parallel Repetition Requires Understanding Foams, Electronic Colloquium on Computational Complexity, Report TR07-043 (ISSN 1433-8092, 14th Year, 43rd Report), 7 May 2007.
OEIS Wiki, A remarkable formula of Ramanujan
FORMULA
Sqrt(Pi*e/2) = A + B with A = 1 + 1/(1*3) + 1/(1*3*5) + 1/(1*3*5*7) + 1/(1*3*5*7*9) + ... = 1.410686134... (see A060196) and B = 1/(1 + 1/(1 + 2/(1 + 3/(1 + 4/(1 + 5/(1 + ...)))))) = 0.65567954241... (see A108088) - (S. Ramanujan)
Equals (sqrt(2)*exp(1/4)*(sum(n>=0, n!/(2*n)! ) - 1))/erf(1/2). - Jean-François Alcover, Mar 22 2013
EXAMPLE
2.066365677...
MATHEMATICA
RealDigits[N[Sqrt[ \[Pi]*\[ExponentialE]/2], 100]][[1]]
PROG
(PARI) { default(realprecision, 20080); x=sqrt(Pi*exp(1)/2); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b059444.txt", n, " ", d)); } \\ Harry J. Smith, Jun 27 2009
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Robert G. Wilson v, Feb 01 2001
EXTENSIONS
Edited by Daniel Forgues, Apr 14 2011
STATUS
approved