0821849409 SHOW MOOCHABLE + ? RELATED SEARCHES > ADVANCED SEARCH > SHOW COVERS + ASIN Copies Jeffrey C. Lagarias The Ultimate Challenge: The 3x+1 Problem 0 Search BookMooch for a book: SEARCH BOOKMOOCH > Search Amazon for a book: amazon.co.uk amazon.de amazon.es amazon.fr amazon.it amazon.cn SEARCH AMAZON >