%I #15 Jun 02 2017 12:27:50
%S 1,2,12,1536,519045120,156130677884314787512320,
%T 12538151702000091464104493325082133822247601116646227522355200
%N Associated with random Penrose-Robinson tilings of the plane.
%C In the Mathematica code, let p=A235857; q=A235858 for convenience.
%H Steven R. Finch, <a href="/A072042/a072042.pdf">Substitution dynamics</a>, January 23, 2014. [Cached copy, with permission of the author]
%H 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 p[n_] := p[n] = 2 p[n-1] q[n-1] - p[n-1]^2 q[n-2];
%t q[n_] := 2 p[n] q[n-1] - p[n-1] p[n-2] q[n-1] q[n-2]^2;
%t p[0] = 1; q[0] = 1; p[1] = 2; q[1] = 4;
%Y Cf. A072042, A235858.
%K nonn
%O 0,2
%A _Steven Finch_, Jan 16 2014