A235202 - OEIS

A235202 as a simple table

n	a(n)
1	1
2	10
3	11
4	20
5	21
6	30
7	31
8	100
9	101
10	110
11	111
12	120
13	121
14	130
15	131
16	1000
17	1001
18	1010
19	1011
20	1020
21	1021
22	1030
23	1031
24	1100
25	1101
26	1110
27	1111
28	1120
29	1121
30	1130
31	1131
32	2000
33	2001
34	2010
35	2011
36	2020
37	2021
38	2030
39	2031
40	2100

[1,10,11,20,21,30,31,100,101,110,111,120,121,130, 131,1000,1001,1010,1011,1020,1021,1030,1031,1100, 1101,1110,1111,1120,1121,1130,1131,2000,2001,2010, 2011,2020,2021,2030,2031,2100]