Concatenation of two or more consecutive positive integers.

Terms

a(0) =12a(1) =23a(2) =34a(3) =45a(4) =56a(5) =67a(6) =78a(7) =89a(8) =123a(9) =234a(10) =345a(11) =456a(12) =567a(13) =678a(14) =789a(15) =910a(16) =1011a(17) =1112a(18) =1213a(19) =1234a(20) =1314a(21) =1415a(22) =1516a(23) =1617a(24) =1718a(25) =1819a(26) =1920a(27) =2021a(28) =2122a(29) =2223