login
Numbers of form 21k+1 or 21k+2 that use only digits 3 and 7.
0

%I #2 Mar 30 2012 17:26:28

%S 337,737,7373,73333,73733,333377,333733,737333,737773,777337,777737,

%T 3333373,3333773,3373337,3373777,3777377,3777733,7337737,7373333,

%U 7373773,7733377,7733777,7777373,33337333,33337733,33377737,33733373

%N Numbers of form 21k+1 or 21k+2 that use only digits 3 and 7.

%Y Cf. A152824 and A152834.

%K base,nonn

%O 1,1

%A _Zak Seidov_, Dec 14 2008, Dec 26 2008