The algorithm used is the one presented
by Greg Fee on ISSAC '90 (using only integer arithmetic in the main loop).
Again, I have verified the previous 1000100-digit value using
LiDIA and text comparison.
Best
Thomas Papanikolaou
Catalan constant to 1500000 digits computed on October 26, 1996
by using a Sun Sparc20 in 7 day 7 hour 14 min 52 sec 71 hsec
The algorithm used is the standard series for Catalan, accelerated
by an Euler transform as shown by