%I #12 Jun 30 2023 14:31:03
%S 1,18,296,4768,76416,1223168,19572736,313171968,5010784256,
%T 80172679168,1282763390976,20524216352768,328387470032896,
%U 5254199554080768,84067192999510016,1345075088529031168,21521201418611982336
%N a(n) = 20*a(n-1) - 64*a(n-2) for n > 1; a(0) = 1, a(1) = 18.
%C lim_{n -> infinity} a(n)/a(n-1) = 16.
%H Vincenzo Librandi, <a href="/A166927/b166927.txt">Table of n, a(n) for n = 0..200</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (20, -64).
%F a(n) = (7*16^n - 4^n)/6.
%F G.f.: (1 - 2*x)/((1-4*x)*(1-16*x)).
%F E.g.f.: (1/6)*(7*exp(16*x) - exp(4*x)). - _G. C. Greubel_, May 28 2016
%t LinearRecurrence[{20, -64}, {1, 18}, 50] (* _G. C. Greubel_, May 28 2016 *)
%o (Magma) [ n le 2 select 17*n-16 else 20*Self(n-1)-64*Self(n-2): n in [1..17] ];
%Y Cf. A166914, A166917.
%K nonn
%O 0,2
%A _Klaus Brockhaus_, Oct 23 2009