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 A214944 #9 Jul 22 2018 08:44:37 %S A214944 0,30,264,1140,3480,8610,18480,35784,64080,107910,172920,265980, %T A214944 395304,570570,803040,1105680,1493280,1982574,2592360,3343620,4259640, %U A214944 5366130,6691344,8266200,10124400,12302550,14840280,17780364,21168840,25055130 %N A214944 Number of squarefree words of length 5 in an (n+1)-ary alphabet. %C A214944 Row 5 of A214943. %H A214944 R. H. Hardin, <a href="/A214944/b214944.txt">Table of n, a(n) for n = 1..210</a> %F A214944 Empirical: a(n) = n^5 + n^4 - 2*n^3 - n^2 + n. %F A214944 Conjectures from _Colin Barker_, Jul 22 2018: (Start) %F A214944 G.f.: 6*x^2*(5 + 14*x + x^2) / (1 - x)^6. %F A214944 a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6. %F A214944 (End) %e A214944 Some solutions for n=2: %e A214944 ..1....2....2....0....1....0....0....0....2....1....2....2....0....2....1....2 %e A214944 ..2....1....1....1....0....1....2....2....1....0....0....0....1....1....2....0 %e A214944 ..0....0....2....2....2....2....1....0....0....2....1....1....0....2....0....2 %e A214944 ..2....2....0....0....1....0....0....1....1....0....2....2....2....0....1....1 %e A214944 ..1....1....2....2....2....1....2....0....2....1....0....1....0....1....0....0 %K A214944 nonn %O A214944 1,2 %A A214944 _R. H. Hardin_, Jul 30 2012