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 A145115 #8 May 23 2024 09:40:04 %S A145115 1,2,4,8,16,32,64,128,256,511,1019,2031,4047,8063,16063,31999,63743, %T A145115 126976,252934,503838,1003630,1999198,3982334,7932670,15801598, %U A145115 31476221,62699509,124895181,248786733,495574269,987166205,1966399741,3916997885,7802519550 %N A145115 Numbers of length n binary words with fewer than 7 0-digits between any pair of consecutive 1-digits. %H A145115 Vincenzo Librandi, <a href="/A145115/b145115.txt">Table of n, a(n) for n = 0..1000</a> %H A145115 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (3, -2, 0, 0, 0, 0, 0, -1, 1). %F A145115 G.f.: (1-x+x^8)/(1-3*x+2*x^2+x^8-x^9). %e A145115 a(9) = 511 = 2^9-1, because 100000001 is the only binary word of length 9 with not less than 7 0-digits between any pair of consecutive 1-digits. %p A145115 a:= n-> (Matrix([[2, 1$8]]). Matrix(9, (i, j)-> if i=j-1 then 1 elif j=1 then [3, -2, 0$5, -1, 1][i] else 0 fi)^n)[1, 2]: seq(a(n), n=0..35); %t A145115 CoefficientList[Series[(1 - x + x^8) / (1 - 3 x + 2 x^2 + x^8 - x^9), {x, 0, 40}], x] (* _Vincenzo Librandi_, Jun 06 2013 *) %Y A145115 7th column of A145111. %K A145115 nonn,easy %O A145115 0,2 %A A145115 _Alois P. Heinz_, Oct 02 2008