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 A214946 #10 Jul 22 2018 11:52:22 %S A214946 0,60,1848,15960,80040,292740,868560,2218608,5062320,10575180, %T A214946 20577480,37769160,66015768,110690580,179077920,280842720,428571360, %U A214946 638388828,930657240,1330760760,1869981960,2586474660,3526338288,4744798800 %N A214946 Number of squarefree words of length 7 in an (n+1)-ary alphabet. %C A214946 Row 7 of A214943. %H A214946 R. H. Hardin, <a href="/A214946/b214946.txt">Table of n, a(n) for n = 1..210</a> %F A214946 Empirical: a(n) = n^7 + n^6 - 4*n^5 - 3*n^4 + 5*n^3 + 2*n^2 - 2*n. %F A214946 Conjectures from _Colin Barker_, Jul 22 2018: (Start) %F A214946 G.f.: 12*x^2*(5 + 114*x + 238*x^2 + 62*x^3 + x^4) / (1 - x)^8. %F A214946 a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8. %F A214946 (End) %e A214946 Some solutions for n=2: %e A214946 ..1....0....1....0....2....2....2....0....1....0....2....2....1....2....2....2 %e A214946 ..0....2....2....1....1....0....0....2....0....1....1....0....2....0....1....1 %e A214946 ..2....0....1....0....2....2....1....1....1....0....2....1....0....2....2....0 %e A214946 ..1....1....0....2....0....1....2....2....2....2....0....0....2....1....0....1 %e A214946 ..2....2....1....0....2....2....1....0....1....0....2....2....1....0....1....2 %e A214946 ..0....0....2....1....1....0....0....1....0....1....1....1....0....2....2....0 %e A214946 ..2....2....1....2....2....1....2....2....1....0....0....0....2....0....1....2 %Y A214946 Cf. A214943. %K A214946 nonn %O A214946 1,2 %A A214946 _R. H. Hardin_, Jul 30 2012