Numbers k such that 0 and 4 occur juxtaposed in the base-10 representation of k but not of k-1.

Terms

a(0) =40a(1) =104a(2) =140a(3) =204a(4) =240a(5) =304a(6) =340a(7) =400a(8) =440a(9) =504a(10) =540a(11) =604a(12) =640a(13) =704a(14) =740a(15) =804a(16) =840a(17) =904a(18) =940a(19) =1004a(20) =1040a(21) =1104a(22) =1140a(23) =1204a(24) =1240a(25) =1304a(26) =1340a(27) =1400a(28) =1440a(29) =1504