The Puzzles of Nobuyuki Yoshigahara

Andy Liu is an Emeritus Professor at the Department of Mathematical and Statistical Sciences, University of Alberta in Edmonton, Canada, where he obtained his Master's degree in Number Theory in 1972, his PhD in Combinatorics in 1976, and a Professional Diploma in Elementary Education in the same year. His initial appointment was in 1980 and he retired in 2013. He was actively involved in mathematics competitions at all levels, including the International Mathematical Olympiad and the International Mathematics Tournament of the Towns. He also ran a mathematics circle for schoolchildren from 1981 to 2012, before handing it over to his successors. His informal interests include literature and history, mechanical puzzles and simulation board games.
George Sicherman is a computer programmer in New Jersey, originally from Buffalo, in New York State, USA. He holds an M.A. in Mathematics and a Ph.D. in Computer Science from the University of Buffalo, having worked in industry till 2009. He has a large website about polyominoes and related figures and often writes computer programs to help other recreational mathematicians. He has designed a variety of puzzles and is the inventor of Sicherman Dice.
Takayuki Yoshigahara is an engineer of an electronics company in Japan. His scientific/professional interests are computer vision and machine learning. His father Nobuyuki Yoshigahara is a great puzzle inventor, and Takayuki has inherited a fondness for solving problems, often using computer algorithms.