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 A338186 #10 Apr 19 2023 18:55:58
%S A338186 2,16,126,1100,9850,88584,797174,7174468,64570098,581130752,
%T A338186 5230176622,47071589436,423644304746,3812798742520,34315188682470,
%U A338186 308836698142004,2779530283277794,25015772549499888,225141952945498718,2026277576509488172,18236498188585393242,164128483697268538856
%N A338186 Expansion of (2-6*x-12*x^2)/((1-x)^2*(1-9*x)).
%C A338186 The locally small terms 4^k in A322469 occur at the positions a(k) (for k = 0..9, and probably in general; cf. conjectures in A322469).
%H A338186 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (11,-19,9).
%F A338186 a(n) = 11*a(n-1) - 19*a(n-2) + 9*a(n-3) for n >= 3.
%e A338186 A322469(a(4)) = A322469(9850) = 256 = 4^4.
%p A338186 f:= gfun:-rectoproc({a(n)=11*a(n-1)-19*a(n-2)+9*a(n-3), a(0)=2, a(1)=16, a(2)=126}, a(n), remember): map(f, [$0..21]);
%t A338186 CoefficientList[Series[(2-6*x-12*x^2)/((1-x)^2*(1-9*x)), {x,0,21}], x]
%o A338186 (PARI) my(x='x+O('x^22)); Vec((2-6*x-12*x^2)/((1-x)^2*(1-9*x)))
%Y A338186 Cf. A322469.
%K A338186 nonn,easy
%O A338186 0,1
%A A338186 _Georg Fischer_, Oct 15 2020