"Imagination is more important than knowledge." Albert Einstein
"Development of Western science is based on two great achievements: the invention of the formal logical system (in Euclidean geometry) by the Greek philosophers, and the discovery of the possibility to find out causal relationships by systematic experiment (during Renaissance)." Albert Einstein (1953)
The 3x + 1 problem (Collatz problem)
- Edited by Jeffrey C. Lagarias, The ultimate challenge: The 3x + 1 problem, AMS (American Mathematical Society), 2010, 348 pp.
- Tomás Oliveira e Silva, Empirical Verification of the 3x+1 and Related Conjectures. In The Ultimate Challenge: The 3x+1 Problem (Book edited by Jeffrey C. Lagarias), pp. 189-207, American Mathematical Society, 2010