Flavius Josephus he was a Jewish historian born into a priestly family from Judea. In the year 64 he would go to Rome to obtain from Nero the release of some Jewish priests captured during the revolts against the Romans, cause for which he is prosecuted and imprisoned. However, he is soon released thanks to the support of Sabina Poppaea, wife of the emperor (once) .
After his return to Jerusalem, in the year 66 the Great Jewish Revolt broke out. He was appointed by the Jerusalem Sanhedrin as commander-in-chief of Galilee, organizing the administration and defense of it. After six weeks of heroic defense of Jotapata against the mighty Roman army, the fortress fell. Joseyo and 40 defenders fled to take refuge on the Masada plateau . Besieged by the Romans, they decided to kill themselves rather than surrender to the enemy.
How to do it? In what order?... Someone proposed standing in a circle and counting 1, 2 and 3; Whoever got 3 would die and so on without counting the dead. Luckily (twice) , Josephus was placed in the 16th place and if you check it, only those located in the 16th and 31st positions can be saved.
To check it, in the old-fashioned way with pencil and paper, you just have to write a circle with 41 numbers and start crossing out number 3, without counting the crossed out (dead) ones in later rounds, saving at the end those located in 16th place and 31. Only a prodigious mental agility (another human calculator?) would have allowed Josejo to choose the place.
When in the end Josejo and another compatriot were left, they decided to capitulate and surrender to the forces of General Vespasiano. Brought before the general, and having lost everything, he dared to predict that Vespasinaus would become the next emperor. In the year 69 the omen was fulfilled and Josephus was released (third time) .
Source:Fun and Curious Mathematics – Malba Tahan