Numbers k such that 0 and 9 occur juxtaposed in the base-10 representation of k but not of k-1.

Terms

a(0) =90a(1) =109a(2) =190a(3) =209a(4) =290a(5) =309a(6) =390a(7) =409a(8) =490a(9) =509a(10) =590a(11) =609a(12) =690a(13) =709a(14) =790a(15) =809a(16) =890a(17) =900a(18) =990a(19) =1009a(20) =1090a(21) =1109a(22) =1190a(23) =1209a(24) =1290a(25) =1309a(26) =1390a(27) =1409a(28) =1490a(29) =1509