The problem appears to be an illustration of an algorithm for multiplying numbers. The sequence 7, 72, 73, 74, 75 appears in the right-hand column, and the terms 2,801, 2×2,801, 4×2,801 appear in the left; the sum on the left is 7×2,801 = 19,607, the same as the sum of the terms on the right. The equality of the two geometric sequences can be stated as the equation (20 + 21 + 22)(70 + 71 + 72 + 73 + 74) = 71 + 72 + 73 + 74 + 75, which relies on the coincidence 20 + 21 + 22 = 7.