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Decimal expansion of 4*Sum_{k=1..5000000} (-1)^(k-1)/(2k-1).
10

%I #13 Feb 06 2015 10:46:33

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

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

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

%N Decimal expansion of 4*Sum_{k=1..5000000} (-1)^(k-1)/(2k-1).

%C An approximation to Pi.

%H J. M. Borwein, P. B. Borwein and K. Dilcher, <a href="http://www.jstor.org/stable/2324715">Pi, Euler numbers and asymptotic expansions</a>, Amer. Math. Monthly, 96 (1989), 681-687.

%H J. M. Borwein and R. M. Corless, <a href="http://www.cecm.sfu.ca/~jborwein/sloane/sloane.html">Review of "An Encyclopedia of Integer Sequences" by N. J. A. Sloane and Simon Plouffe</a>, SIAM Review, 38 (1996), 333-337.

%e 3.1415924535897932384646433832795027841971693993873058209749418223...

%Y Cf. A000796, A216542, A013706, A216543, A216544, A216545, A013705, A216546, A216547, A216548.

%Y Cf. also A195793.

%K cons,nonn

%O 1,1

%A _N. J. A. Sloane_, Sep 08 2012