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 A177293 #9 Jan 18 2016 18:40:35 %S A177293 1,1,20,1680,369600,37850400,2626916040,171548183912,12520880883034, %T A177293 920942694050320,65368388837752640 %N A177293 Number of permutations of 3 copies of 1..n with all adjacent differences <= 3 in absolute value. %C A177293 a(n) = (3n)!/6^n for n<=4. %Y A177293 Cf. A014606. %K A177293 nonn %O A177293 0,3 %A A177293 _R. H. Hardin_, May 06 2010 %E A177293 a(10) from _Alois P. Heinz_, Jan 18 2016