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 A235857 #15 Jun 02 2017 12:27:50 %S A235857 1,2,12,1536,519045120,156130677884314787512320, %T A235857 12538151702000091464104493325082133822247601116646227522355200 %N A235857 Associated with random Penrose-Robinson tilings of the plane. %C A235857 In the Mathematica code, let p=A235857; q=A235858 for convenience. %H A235857 Steven R. Finch, <a href="/A072042/a072042.pdf">Substitution dynamics</a>, January 23, 2014. [Cached copy, with permission of the author] %H A235857 C. Godrèche and J. M. Luck, <a href="http://dx.doi.org/10.1007/BF01042590">Quasiperiodicity and randomness in tilings of the plane</a>, J. Statist. Phys. 55 (1989) 1-28. %t A235857 p[n_] := p[n] = 2 p[n-1] q[n-1] - p[n-1]^2 q[n-2]; %t A235857 q[n_] := 2 p[n] q[n-1] - p[n-1] p[n-2] q[n-1] q[n-2]^2; %t A235857 p[0] = 1; q[0] = 1; p[1] = 2; q[1] = 4; %Y A235857 Cf. A072042, A235858. %K A235857 nonn %O A235857 0,2 %A A235857 _Steven Finch_, Jan 16 2014