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 A177308 #5 Mar 02 2016 11:19:29 %S A177308 1,1,3432,399072960,5188083048720,39956935830445136, %T A177308 452976400962846092338 %N A177308 Number of permutations of 7 copies of 1..n with all adjacent differences <= 2 in absolute value. %C A177308 a(n) = (7n)!/5040^n for n<=3. %Y A177308 Cf. A172603. %K A177308 nonn %O A177308 0,3 %A A177308 _R. H. Hardin_, May 06 2010