glibg10b, 7 months ago

Explanation:

In decimal (DEC), we count to 9 before adding a new digit. For example, the number after 9 is 10, and the number after 19 is 20.

In octal (OCT), we count to 7 before adding a new digit. The number after 7 is 10 and the number after 17 is 20.

DEC	OCT
0	0
1	1
2	2
3	3
4	4
5	5
6	6
7	7
8	10
9	11
10	12
11	13
12	14
13	15
14	16
15	17
16	20
17	21
18	22
19	23
20	24
21	25
22	26
23	27
24	30
25	31