March 15, 2025Math Puzzle: Finish the CycleBy Heinrich Hemme Eight numbers emerge in sequence according to a certain system. One number is unknown. Can you figure out what it should be?Each number is the sum of the squares of the digits of its predecessor.42 = 16 12 + 62 = 37 32 + 72 = 58 52 + 82 = 89 82 + 92 = 145 12 + 42 + 52 = 42 42 + 22 = 20 22 + 02 = 4The missing number is 20.Wed love to hear from you! E-mail us at games@sciam.com to share your experience.This puzzle originally appeared in Spektrum der Wissenschaft and was reproduced with permission.0