A216478 a(n) is the least multiple of n which uses only digits 1 and 2. a(n) = -1 if no such multiple exists.
1, 2, 12, 12, -1, 12, 21, 112, 12222, -1, 11, 12, 221, 112, -1, 112, 221, 12222, 1121, -1, 21, 22, 12121, 2112, -1, 1222, 21222, 112, 12122, -1, 11222, 2112, 1122, 1122, -1, 22212, 111, 12122, 111111, -1, 11111, 12222, 12212, 2112, -1, 122222, 1222, 2112, 11221, -1, 1122, 21112, 212, 21222, -1, 112, 212211, 12122, 1121
Offset: 1