Here are various mathematical constants: catalan -- Catalan's constant, 30,000 digits, by Simon Plouffe exp1 -- exp(1), 250,000 digits, by Simon Plouffe feigenbaums -- Feigenbaum's constants alpha and delta, by Jeffrey Shallit pi -- pi, 1,250,000 digits sqrt2 -- sqrt(2), 1 million digits, by Project Gutenberg