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 A124721 #4 Aug 07 2015 16:13:33 %S A124721 2,8,26,80,224,596,1536,3840,9384,22528,53248,124240,286720,655360, %T A124721 1485472,3342336,7471104,16602432,36700160,80740352,176859776, %U A124721 385875968,838860800,1817531648,3925868544,8455716864,18164132352,38923141120 %N A124721 Number of ternary Lyndon words with exactly three 1's. %H A124721 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (6,-12,10,-12,24,-16). %F A124721 G.f.: 2*x^4*(x - 1)^2/(1-2*x^3)/(1-2*x)^3 = (x^3/(1-2*x)^3-x^3/(1-2*x^3))/3 %e A124721 a(5) = 8 because 11122, 11212, 11123, 11132, 11213, 11312, 11133, 11313 are all ternary Lyndon words of length 5 with three 1's %Y A124721 Cf. A051168, A027376, A124720, A124722, A124723. %K A124721 nonn,easy %O A124721 4,1 %A A124721 _Mike Zabrocki_, Nov 05 2006