The sum of all the numbers in the sequence 1,2,3,... 10000? The answer is 180001

The sum of all the numbers in the sequence 1,2,3,... 10000? The answer is 180001

All the numbers are represented by five digits. Adding 0 and 0 before less than five digits will not affect the sum of the numbers. 1 means that the numbers on 00001 digits are 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 A group of 10 cycles, 1000 groups, sum of numbers = 45 × 1000 = 45000, the numbers on the ten digits are 0, 0 (9), 1,1 (10), 2, 2 ...