A216543 - OEIS

A216543

Decimal expansion of 4*Sum_{k=1..50000} (-1)^(k-1)/(2k-1).

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

(list; constant; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

An approximation to Pi.

LINKS

Table of n, a(n) for n=1..125.

J. M. Borwein, P. B. Borwein, and K. Dilcher, Pi, Euler numbers and asymptotic expansions, Amer. Math. Monthly, 96 (1989), 681-687.

J. M. Borwein and R. M. Corless, Review of "An Encyclopedia of Integer Sequences" by N. J. A. Sloane and Simon Plouffe, SIAM Review, 38 (1996), 333-337.

EXAMPLE

3.14157265358979523846264238327950410419716662937511592517489...

MATHEMATICA