Nonnegative numbers with digits in descending order that differ exactly by 1.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =8a(9) =9a(10) =10a(11) =21a(12) =32a(13) =43a(14) =54a(15) =65a(16) =76a(17) =87a(18) =98a(19) =210a(20) =321a(21) =432a(22) =543a(23) =654a(24) =765a(25) =876a(26) =987a(27) =3210a(28) =4321a(29) =5432