A231875 - OEIS

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A231875 as a simple table

n	a(n)
1	2
2	12
3	21
4	22
5	112
6	121
7	122
8	211
9	212
10	221
11	222
12	1112
13	1121
14	1122
15	1211
16	1212
17	1221
18	1222
19	2111
20	2112
21	2121
22	2122
23	2211
24	2212
25	2221
26	2222

[2,12,21,22,112,121,122,211,212,221,222,1112,1121, 1122,1211,1212,1221,1222,2111,2112,2121,2122,2211, 2212,2221,2222]