Concatenation of 3 or more numbers in arithmetic progression with positive common difference.

Terms

a(0) =123a(1) =135a(2) =147a(3) =159a(4) =234a(5) =246a(6) =258a(7) =345a(8) =357a(9) =369a(10) =456a(11) =468a(12) =567a(13) =579a(14) =678a(15) =789a(16) =1234a(17) =1357a(18) =1611a(19) =1713a(20) =1815a(21) =1917a(22) =2345a(23) =2468a(24) =2610a(25) =2712a(26) =2814a(27) =2916a(28) =3456a(29) =3579