Exactly 4 digits from {1,2,3,4,5,6,7,8,9} can precede a(n) to form a lucky number.

Terms

a(0) =9a(1) =29a(2) =35a(3) =83a(4) =85a(5) =93a(6) =123a(7) =173a(8) =211a(9) =233a(10) =249a(11) =339a(12) =379a(13) =419a(14) =427a(15) =471a(16) =473a(17) =487a(18) =501a(19) =551a(20) =575a(21) =587a(22) =621a(23) =625a(24) =675a(25) =687a(26) =763a(27) =773a(28) =787a(29) =801