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 A177305 #5 Mar 02 2016 11:16:18 %S A177305 1,1,924,17153136,47768769048,83659800759150,202929004783993742 %N A177305 Number of permutations of 6 copies of 1..n with all adjacent differences <= 2 in absolute value. %C A177305 a(n) = (6n)!/720^n for n<=3. %Y A177305 Cf. A248814. %K A177305 nonn %O A177305 0,3 %A A177305 _R. H. Hardin_, May 06 2010