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 A170810 #3 Mar 31 2012 12:35:36 %S A170810 1,2,4,12,40,116,200,444,760,2160,4872,11932,29252,71708,191356, %T A170810 536908,1607592,5184252,17331516,61597568,228854684,891958912 %N A170810 Number of permutations of 1..n with all differences of elements separated by distances 1 through 4 being respectively unique. %C A170810 (Empirical) Equals A008404 for n<=2m+2, where m is the maximum difference separation 4. %K A170810 nonn %O A170810 1,2 %A A170810 _R. H. Hardin_ Dec 02 2009