login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

a(n) is the least multiple of n which uses only digit 2, or a(n) = -1 if no such multiple exists.
2

%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