The square root of 2 equals 1.41421356237… Multiply this successively by 1, by 2, by 3, by 4 and so on, and write down the integer part of each result. Beneath this sequence, make a second list of the numbers missing from the first sequence.

Then the differences between the upper and lower numbers in these pairs are 2, 4, 6, 8, 10, 12, 14, 16, 18…