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A152853
Numbers of form 21k+1 or 21k+2 that use only digits 3 and 7.
0
337, 737, 7373, 73333, 73733, 333377, 333733, 737333, 737773, 777337, 777737, 3333373, 3333773, 3373337, 3373777, 3777377, 3777733, 7337737, 7373333, 7373773, 7733377, 7733777, 7777373, 33337333, 33337733, 33377737, 33733373
OFFSET
1,1
CROSSREFS
Cf. A152824 and A152834.
Sequence in context: A339480 A214492 A157999 * A142830 A160069 A201852
KEYWORD
base,nonn
AUTHOR
Zak Seidov, Dec 14 2008, Dec 26 2008
STATUS
approved