As we are subtracting 2 continuously from the resulting numbers, get a progression with a common difference of 2 and we need to multiply the sum by 2 to get hash number. For example 5: (3 + 1) × 2 = 8. 19 : (17 + 15 + 13 + ......+1) × 2 = 81 × 2 = 162. 7 : (5 + 3 + 1) × 2 = 18. 15: (13 + 11 + 9 + 7 + 5 + 3 + 1) × 2 = 98. Sum of the hash numbers = 278.