This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A138142 #19 Apr 15 2014 11:41:18
%S A138142 0,1,2,3,4,5,6,7,8,9,10,21,32,43,54,65,76,87,98,210,321,432,543,654,
%T A138142 765,876,987,3210,4321,5432,6543,7654,8765,9876,43210,54321,65432,
%U A138142 76543,87654,98765,543210,654321,765432,876543,987654
%N A138142 Nonnegative numbers with digits in descending order that differ exactly by 1.
%C A138142 This finite sequence has 55 members. The last member is 9876543210. There are 11-k members with k digits. See A052016 for primes in this sequence. All members with 3 or more digits are straight-line numbers A135643.
%e A138142 Last 10 members of this finite sequence:
%e A138142 a(45)=6543210
%e A138142 a(46)=7654321
%e A138142 a(47)=8765432
%e A138142 a(48)=9876543
%e A138142 a(49)=76543210
%e A138142 a(50)=87654321
%e A138142 a(51)=98765432
%e A138142 a(52)=876543210
%e A138142 a(53)=987654321
%e A138142 a(54)=9876543210
%t A138142 fQ[n_]:=Module[{id=IntegerDigits[n]}, n<10 || Union[Differences[id]]=={-1}]; Select[Range[0, 100000], fQ] (* _Vladimir Joseph Stephan Orlovsky_, Dec 29 2010 *)
%t A138142 Sort[Flatten[With[{t=Range[9,0,-1]},Table[FromDigits/@Partition[t,n,1],{n,10}]]]] (* _Harvey P. Dale_, Oct 31 2013 *)
%Y A138142 Cf. A052016, A135643, A138141.
%K A138142 base,easy,fini,nonn
%O A138142 1,3
%A A138142 _Omar E. Pol_, Mar 19 2008
%E A138142 Examples corrected by _Omar E. Pol_, Dec 06 2008