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 A126519 #7 Mar 31 2012 12:35:06
%S A126519 1,24,196,1644,13916,118416,1010892,8648028,74086762,635291688,
%T A126519 5451042614,46791744232,401773647392,3450448765596,29636332554924,
%U A126519 254571572184234,2186853928177032,18786503501683672,161392382824498244
%N A126519 Number of base 24 n-digit numbers with adjacent digits differing by four or less.
%C A126519 [Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4
%o A126519 (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>4)+($[i+1]`-$[i]`>4))
%Y A126519 Cf. Base 24 differing by three or less A126492, two or less A126411, one or less A126378.
%K A126519 nonn,base
%O A126519 0,2
%A A126519 _R. H. Hardin_, Dec 28 2006