Numbers which can be expressed as the product of numbers made of only sevens.

Terms

a(0) =1a(1) =7a(2) =49a(3) =77a(4) =343a(5) =539a(6) =777a(7) =2401a(8) =3773a(9) =5439a(10) =5929a(11) =7777a(12) =16807a(13) =26411a(14) =38073a(15) =41503a(16) =54439a(17) =59829a(18) =77777a(19) =117649a(20) =184877a(21) =266511a(22) =290521a(23) =381073a(24) =418803a(25) =456533a(26) =544439a(27) =598829a(28) =603729a(29) =777777