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 A351529 #14 Jun 10 2024 08:53:05
%S A351529 0,0,1,7,40,205,991,4612,20905,92935,407056,1762117,7556095,32148940,
%T A351529 135892321,571232647,2389810360,9956870845,41335010911,171055514452,
%U A351529 705891052825,2905717608775,11934337612576,48918212175157,200149835407615,817572886925980
%N A351529 The number of quaternary strings of length n containing 00.
%H A351529 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7,-9,-12).
%F A351529 G.f.: x^2 / ( (4*x-1)*(3*x^2+3*x-1) ).
%F A351529 a(n) = 4^n - A125145(n).
%t A351529 LinearRecurrence[{7,-9,-12},{0,0,1},30] (* _Harvey P. Dale_, Feb 27 2023 *)
%Y A351529 Cf. A008466 (2-ary), A186244 (3-ary), A351530 (5-ary), A125145 (not containing 00).
%K A351529 nonn,easy
%O A351529 0,4
%A A351529 _R. J. Mathar_, Feb 13 2022