Sum of digits = 7 times number of digits.

Terms

a(0) =7a(1) =59a(2) =68a(3) =77a(4) =86a(5) =95a(6) =399a(7) =489a(8) =498a(9) =579a(10) =588a(11) =597a(12) =669a(13) =678a(14) =687a(15) =696a(16) =759a(17) =768a(18) =777a(19) =786a(20) =795a(21) =849a(22) =858a(23) =867a(24) =876a(25) =885a(26) =894a(27) =939a(28) =948a(29) =957