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 A093341 Decimal expansion of "lemniscate case". 10
 1, 8, 5, 4, 0, 7, 4, 6, 7, 7, 3, 0, 1, 3, 7, 1, 9, 1, 8, 4, 3, 3, 8, 5, 0, 3, 4, 7, 1, 9, 5, 2, 6, 0, 0, 4, 6, 2, 1, 7, 5, 9, 8, 8, 2, 3, 5, 2, 1, 7, 6, 6, 9, 0, 5, 5, 8, 5, 9, 2, 8, 0, 4, 5, 0, 5, 6, 0, 2, 1, 7, 7, 6, 8, 3, 8, 1, 1, 9, 9, 7, 8, 3, 5, 7, 2, 7, 1, 8, 6, 1, 6, 5, 0, 3, 7, 1, 8, 9, 7, 2, 7, 7, 7, 7 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions with Formulas, Graphs and Mathematical Tables, 9th printing. New York: Dover, 1972, Section 18.14.7, p. 658. Jonathan Borwein & Peter Borwein, A Dictionary of Real Numbers. Pacific Grove, California: Wadsworth & Brooks/Cole Advanced Books & Software (1990) p. iii Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 6.1 Gauss' Lemniscate Constant, p. 421. LINKS Harry J. Smith, Table of n, a(n) for n = 1..5000 M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy]. M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions with Formulas, Graphs and Mathematical Tables, Section 18.14.7, p. 658. G. Mingari Scarpello, D. Ritelli, On computing some special values of hypergeometric functions, arXiv:1212.0251, eq. (4.1) Eric Weisstein's World of Mathematics, Lemniscate Case. FORMULA GAMMA(1/4)^2/(4*(Pi)^(1/2)). - Pab Ter (pabrlos(AT)yahoo.com), May 24 2004 Also equals ellipticK(1/sqrt(2)) = Pi/2*hypergeom([1/2,1/2],[1],1/2), or also the smallest positive root of cs(x/sqrt(2)|-1), where cs is the Jacobi elliptic function, or also the real half-period of the Weierstrass Pe function (Cf. Finch p. 422). - Jean-François Alcover, Apr 30 2013, updated Aug 01 2014 From Peter Bala, Feb 22 2015: (Start) Equals int {x = 0..inf} 1/sqrt(1 + x^4) dx = 2 * int {x = 0..1} 1/sqrt(1 + x^4) dx = sqrt(2) * int {x = 0..1} 1/sqrt(1 - x^4) dx. Equals 2 * Sum {n >= 0} (-1/4)^n * binomial(2*n,n) * 1/(4*n + 1). (End) EXAMPLE 1.854074677301371918433850347195260046217598823521766905585928045056021... MAPLE evalf( EllipticK(1/sqrt(2)) ); # R. J. Mathar, Aug 28 2013 MATHEMATICA RealDigits[ N[ Gamma[1/4]^2 / (4*Sqrt[Pi]), 105]][[1]] (* Jean-François Alcover, Oct 04 2011 *) RealDigits[N[EllipticK[1/2], 105]][[1]] (* Vaclav Kotesovec, Feb 22 2015 *) PROG (PARI) { allocatemem(932245000); default(realprecision, 5080); x=gamma(1/4)^2/(4*(Pi)^(1/2)); for (n=1, 5000, d=floor(x); x=(x-d)*10; write("b093341.txt", n, " ", d)); } \\ Harry J. Smith, Jun 19 2009 (PARI) Pi/agm(sqrt(2), 2) \\ Charles R Greathouse IV, Feb 04 2015 CROSSREFS Cf. A064853, A062539, A105372, A153396. Sequence in context: A081885 A019609 A334502 * A134973 A030437 A200290 Adjacent sequences:  A093338 A093339 A093340 * A093342 A093343 A093344 KEYWORD cons,nonn,easy AUTHOR Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Apr 26 2004 EXTENSIONS More terms from Pab Ter (pabrlos(AT)yahoo.com), May 24 2004 STATUS approved

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Last modified June 22 04:06 EDT 2021. Contains 345367 sequences. (Running on oeis4.)