Positive integers with digits in decreasing order that differ by 2.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =20a(10) =31a(11) =42a(12) =53a(13) =64a(14) =75a(15) =86a(16) =97a(17) =420a(18) =531a(19) =642a(20) =753a(21) =864a(22) =975a(23) =6420a(24) =7531a(25) =8642a(26) =9753a(27) =86420a(28) =97531