Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #9 Sep 18 2012 13:13:35
%S 2,2,222,-1,-1,222,222222,-1,222222222,-1,22,-1,222222,222222,-1,-1,
%T 2222222222222222,222222222,222222222222222222,-1,222222,22,
%U 2222222222222222222222,-1,-1,222222,222222222222222222222222222,-1,2222222222222222222222222222,-1,222222222222222,-1,222222,2222222222222222,-1,-1,222,222222222222222222,222222,-1,22222,222222
%N a(n) is the least multiple of n which uses only digit 2, or a(n) = -1 if no such multiple exists.
%Y Cf. A004290, A078241, A079339, A181060, A181061, A216812.
%K sign,base
%O 1,1
%A _V. Raman_, Sep 07 2012