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 A121196 #11 Oct 19 2017 10:38:28 %S A121196 1,11,114,1519,20769 %N A121196 Consider the tiling of the plane with squares of two different sizes as in Fig. 2.4.2(g) of Grünbaum and Shephard, p. 74. a(n) is the number of connected figures that can be formed on this tiling, from n tiles, each composed of a big square and an adjacent little square. %C A121196 The Zucca web site calls these figures "n-PairSquares". %D A121196 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. %H A121196 Livio Zucca, <a href="http://www.iread.it/lz/polymultiforms2.html">PolyMultiForms</a> %Y A121196 Cf. A121195, A121197, A121198. %K A121196 nonn %O A121196 1,2 %A A121196 _N. J. A. Sloane_, Aug 17 2006 %E A121196 Better definition from _Don Reble_, Aug 17 2007