Number reasoning, the most difficult problem in the world
It should be 42
The latter is the sum of the squares of the digits of the former
For example, 16 = 4 square
37 = 1 square + 6 square
58 = 3 square + 7 square
wait
therefore
Next: 1 square + 4 square + 5 square = 42
Next: 4 square + 2 square = 20
Next: 2 square = 4
Further down the loop