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 A297183 #6 Dec 28 2017 06:42:39 %S A297183 0,0,2,4,10,20,44,92,194,396,820,1684,3432,6972,14144,28636,57890, %T A297183 116828,235500,474304,954444,1919364,3857548,7748888,15558988, %U A297183 31229384,62662088,125696800,252079196,505423476,1013189208,2030729700,4069562810,8154257184,16336840080,32726819744,65553540096 %N A297183 Number of open binary words of length n. %C A297183 Equals 2^n - A226452(n). %H A297183 Gabriele Fici, <a href="http://bulletin.eatcs.org/index.php/beatcs/article/viewFile/508/497">Open and Closed Words</a>, in Giovanni Pighizzini, ed., The Formal Language Theory Column, Bulletin of EATCS, 2017. %Y A297183 Cf. A226452. %K A297183 nonn %O A297183 0,3 %A A297183 _N. J. A. Sloane_, Dec 28 2017