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 A126526 #7 Mar 31 2012 12:35:06
%S A126526 1,31,259,2211,19019,164343,1424235,12368115,107567215,936593437,
%T A126526 8162112673,71178552195,621048996119,5421039243545,47334756754423,
%U A126526 413416811445643,3611458265770503,31553302705135081,275714829055325817
%N A126526 Number of base 31 n-digit numbers with adjacent digits differing by four or less.
%C A126526 [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 A126526 (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 A126526 Cf. Base 31 differing by three or less A126499, two or less A126418, one or less A126385.
%K A126526 nonn,base
%O A126526 0,2
%A A126526 _R. H. Hardin_, Dec 28 2006