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 A170811 #3 Mar 31 2012 12:35:36 %S A170811 1,2,4,12,40,116,200,444,760,2160,4368,7852,14040,24284,42312,79340, %T A170811 152764,320920,688780,1577244,3763512,9412948 %N A170811 Number of permutations of 1..n with all differences of elements separated by distances 1 through 5 being respectively unique. %C A170811 (Empirical) Equals A008404 for n<=2m+2, where m is the maximum difference separation 5. %K A170811 nonn %O A170811 1,2 %A A170811 _R. H. Hardin_ Dec 02 2009