a(n) is the base-(-10) representation of a(n-1) read in base 10, starting from -1.

Terms

a(0) =-1a(1) =19a(2) =199a(3) =219a(4) =399a(5) =419a(6) =599a(7) =619a(8) =799a(9) =819a(10) =999a(11) =19019a(12) =21199a(13) =39219a(14) =41399a(15) =59419a(16) =61599a(17) =79619a(18) =81799a(19) =99819a(20) =1901999a(21) =2118019a(22) =3922199a(23) =4138219a(24) =5942399a(25) =6158419a(26) =7962599a(27) =8178619a(28) =9982799a(29) =190198819