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 A126499 #5 Mar 31 2012 12:35:06
%S A126499 1,31,205,1379,9333,63399,431717,2944947,20115561,137543107,941258689,
%T A126499 6445801999,44166431335,302771722951,2076414065529,14244985903467,
%U A126499 97754711626643,671000257052461,4606822746884183,31634499742407797
%N A126499 Number of base 31 n-digit numbers with adjacent digits differing by three or less.
%C A126499 [Empirical] a(base,n)=a(base-1,n)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3
%o A126499 (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))
%Y A126499 Cf. Base 31 differing by two or less A126418, one or less A126385.
%K A126499 nonn,base
%O A126499 0,2
%A A126499 _R. H. Hardin_, Dec 27 2006