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 A235858 #14 Jun 02 2017 12:27:53 %S A235858 1,4,88,236544,211790340292608,56686233255830734129089579999779880960 %N A235858 Associated with random Penrose-Robinson tilings of the plane. %C A235858 In the Mathematica code, let p=A235857; q=A235858 for convenience. %H A235858 Steven R. Finch, <a href="/A072042/a072042.pdf">Substitution dynamics</a>, January 23, 2014. [Cached copy, with permission of the author] %H A235858 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 A235858 p[n_] := p[n] = 2 p[n-1] q[n-1] - p[n-1]^2 q[n-2]; %t A235858 q[n_] := 2 p[n] q[n-1] - p[n-1] p[n-2] q[n-1] q[n-2]^2; %t A235858 p[0] = 1; q[0] = 1; p[1] = 2; q[1] = 4; %Y A235858 Cf. A072042, A235857. %K A235858 nonn %O A235858 0,2 %A A235858 _Steven Finch_, Jan 16 2014