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%I #3 Sep 10 2012 23:23:43
%S 1,2,12,12,-1,12,21,112,12222,-1,11,12,221,112,-1,112,221,12222,1121,
%T -1,21,22,12121,2112,-1,1222,21222,112,12122,-1,11222,2112,1122,1122,
%U -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
%N a(n) is the least multiple of n which uses only digits 1 and 2. a(n) = -1 if no such multiple exists.
%Y Cf. A004290, A079339, A181060, A181061.
%K sign,base
%O 1,2
%A _V. Raman_, Sep 07 2012