A086465 Decimal expansion of (5 + 4*sqrt(5)*arcsch(2))/25.
3, 7, 2, 1, 6, 3, 5, 7, 6, 3, 8, 5, 6, 0, 1, 6, 1, 5, 5, 5, 5, 7, 7, 3, 2, 9, 3, 1, 8, 0, 2, 4, 2, 1, 7, 0, 1, 6, 9, 8, 2, 8, 2, 7, 3, 0, 1, 6, 1, 1, 5, 8, 6, 1, 9, 0, 2, 8, 0, 2, 4, 4, 1, 5, 9, 7, 0, 2, 4, 4, 8, 6, 1, 8, 4, 4, 5, 2, 7, 8, 4, 5, 4, 4, 5, 9, 6, 1, 0, 5, 8, 7, 8, 8, 8, 7, 9, 8, 2
Offset: 0
Examples
0.37216357638560161555577...
Links
- D. H. Lehmer, Interesting series involving the Central Binomial Coefficient, Am. Math. Monthly 92, No. 7 (1985) 449-457.
- Eric Weisstein's World of Mathematics, Central Binomial Coefficient.
- Wikipedia, Inverse hyperbolic function: Series expansions.
- Index entries for transcendental numbers.
Programs
-
Maple
2/625*(14*sqrt(5)*log((1+sqrt(5))/2)+5) ; # R. J. Mathar, Mar 04 2009
-
Mathematica
RealDigits[(5 + 4*Sqrt[5]*ArcSinh[1/2])/25, 10, 120][[1]] (* Amiram Eldar, May 25 2023 *)
-
PARI
suminf(n=1, (-1)^(n-1)/binomial(2*n,n)) \\ Michel Marcus, Jul 31 2015
-
PARI
asinh(.5)*sqrt(5)*.16+.2 \\ Use \p99 to get 99 digits. - M. F. Hasler, Jul 31 2015
Formula
Equals Sum_{n>=1} (-1)^(n-1)/binomial(2*n,n).
Extensions
Corrected definition and digits by a factor of 25/24. - R. J. Mathar, Mar 04 2009