Numbers whose decimal expansion is a concatenation of 4 consecutive increasing nonnegative numbers.

Terms

a(0) =1234a(1) =2345a(2) =3456a(3) =4567a(4) =5678a(5) =6789a(6) =78910a(7) =891011a(8) =9101112a(9) =10111213a(10) =11121314a(11) =12131415a(12) =13141516a(13) =14151617a(14) =15161718a(15) =16171819a(16) =17181920a(17) =18192021a(18) =19202122a(19) =20212223a(20) =21222324a(21) =22232425a(22) =23242526a(23) =24252627a(24) =25262728a(25) =26272829a(26) =27282930a(27) =28293031a(28) =29303132a(29) =30313233