Numbers of form 7^i*9^j, with i, j >= 0.

Terms

a(0) =1a(1) =7a(2) =9a(3) =49a(4) =63a(5) =81a(6) =343a(7) =441a(8) =567a(9) =729a(10) =2401a(11) =3087a(12) =3969a(13) =5103a(14) =6561a(15) =16807a(16) =21609a(17) =27783a(18) =35721a(19) =45927a(20) =59049a(21) =117649a(22) =151263a(23) =194481a(24) =250047a(25) =321489a(26) =413343a(27) =531441a(28) =823543a(29) =1058841