Numbers whose digits are nonzero, consecutive, and all increasing or all decreasing.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =12a(10) =21a(11) =23a(12) =32a(13) =34a(14) =43a(15) =45a(16) =54a(17) =56a(18) =65a(19) =67a(20) =76a(21) =78a(22) =87a(23) =89a(24) =98a(25) =123a(26) =234a(27) =321a(28) =345a(29) =432