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Additional REFERENCES:
Catalan constant is: sum((-1)**(n+1)/(2*n-1)**2,n=1..infinity) also known
under the name beta(2), see ?catalan in Maple for more details.
The previous record was 200000 digits, also from Thomas Papanikolaou
and before that: 100000 digits
was due to Greg Fee and Simon Plouffe on August 14, 1996,
by using a SGI r10000 Power Challenge with 194 Mhz in 5.63 hours
and the standard implementation of Catalan on MapleV, Release 4.
(which uses Greg's idea).
Euler Tranform: References, Abramowitz and Stegun, formula 3.6.27
page 16 in Handbook of Mathematical Functions and Tables, Dover 1964.
Ramanujan Notebooks, part I formula 34.1 of page 293.
The series used is by putting x--> -1/2 . In other
words the formula used is: the ordinary formula for Catalan
sum((-1)**(n+1)/(2*n+1)**2,n=0..infinity)
and then you apply the Euler Transform to it.
Computation of Catalan's constant using Ramanujan's Formula, by
Greg Fee, ACM 1990, Proceedings of the ISAAC conference, 1990, p. 157.