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 A383740 #15 May 08 2025 07:25:40
%S A383740 4,12,204,2772,39236,551532,7761996,109216308,1536797956,21624369228,
%T A383740 304278011724,4281516425748,60245508232004,847718631046572,
%U A383740 11928306344398284,167844007448966772,2361744410638758916,33232265756370284172,467613464999874177996,6579820775754484587348
%N A383740 a(0) = 4; a(n) = Pell(4*n)/Pell(n) for n > 0.
%H A383740 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (12,30,-12,-1).
%F A383740 a(n) = 12*a(n-1) + 30*a(n-2) - 12*a(n-3) - a(n-4).
%F A383740 G.f.: 4 * (1-9*x-15*x^2+3*x^3)/((1+2*x-x^2) * (1-14*x-x^2)).
%t A383740 a[n_] := Fibonacci[4*n, 2]/Fibonacci[n, 2]; a[0] = 4; Array[a, 20, 0] (* _Amiram Eldar_, May 08 2025 *)
%o A383740 (PARI) my(N=30, x='x+O('x^N)); Vec(4*(1-9*x-15*x^2+3*x^3)/((1+2*x-x^2)*(1-14*x-x^2)))
%Y A383740 Row n=4 of A383742.
%Y A383740 Cf. A000129, A099930.
%K A383740 nonn,easy
%O A383740 0,1
%A A383740 _Seiichi Manyama_, May 07 2025