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 A255374 #17 Aug 25 2016 17:15:08
%S A255374 0,0,0,0,1,18,261,3420,42300,503991,5849757,66595383,746925399,
%T A255374 8278904070,90884885481,989800742916,10707460718526,115168484215116,
%U A255374 1232617054343121,13135427089598511,139446180653268195,1475374347592901460,15562803326717545290
%N A255374 Number of strings of n decimal digits that contain at least one string of exactly 4 consecutive "0" digits.
%H A255374 Alois P. Heinz, <a href="/A255374/b255374.txt">Table of n, a(n) for n = 0..1000</a>
%H A255374 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (20,-100,0,0,-9,99,-90).
%F A255374 a(0) = a(1) = a(2) = a(3) = 0, a(4) = 1, a(n) = 9*(10^(n-5) - a(n-5) + sum_{i=4..n-1} a(i)) for n>=5.
%F A255374 G.f.: x^4*(x-1)^2/((10*x-1)*(9*x^6-9*x^5+10*x-1)). - _Alois P. Heinz_, Feb 26 2015
%Y A255374 Cf. A255371-A255373 (for the k=1 through k=3 cases of "exactly k consecutive '0' digits"), A255375-A255380 (for the cases k=5 through k=10).
%K A255374 nonn,base,easy
%O A255374 0,6
%A A255374 _Jon E. Schoenfield_, Feb 22 2015