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.

Catalan constant to 300000 digits

------------------------------------------------------------------------

.91596559417721901505460351493238411077414937428167213426649811962176301977625
476947935651292611510624857442261919619957903589880332585905943159473748115840
699533202877331946051903872747816408786590902470648415216300022872764094238825
995774150881639747025248201156070764488380787337048990086477511322599713434074
854075532307685653357680958352602193823239508007206803557610482357339423191498
298361899770690364041808621794110191753274314997823397610551224779530324875371
878665828082360570225594194818097535097113157126158042427236364398500173828759
779765306837009298087388749561089365977194096872684444166804621624339864838916
280448281506273022742073884311722182721904722558705319086857354234985394983099
191159673884645086151524996242370437451777372351775440708538464401321748392999
947572446199754961975870640074748707014909376788730458699798606448749746438720
623851371239273630499850353922392878797906336440323547845358519277777872709060
830319943013323167124761587097924554791190921262018548039639342434956537596739
494354730014385180705051250748861328564129344959502298722983162894816461622573
989476231819542006607188142759497559958983637303767533853381354503127681724011
814072153468831683568168639327293677586673925839540618033387830687064901433486
017298106992179956530958187157911553956036689036990493966753843775810493189955
385516262196253316804016273752130120940604538795076053827123197467900882369178
615573389124417223833938148120775994298491724397668575632718068808279982979378
849432724934657607490543874819526813074437046294635892810276531705076547974494
83994895947709278859119584872412786608408855459782381249226050561009458448