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 A118885 #5 Jul 26 2022 12:04:51 %S A118885 0,0,0,0,1,4,12,32,78,180,400,864,1827,3800,7800,15840,31884,63704, %T A118885 126480,249760,490885,960828,1873828,3642560,7060314,13649196, %U A118885 26324704,50662464,97309767,186571248,357119472,682524224,1302589016,2482706544 %N A118885 Number of binary sequences of length n containing exactly one subsequence 0011. %C A118885 Column 1 of A118884. %H A118885 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4,0,-2,4,0,0,-1). %F A118885 G.f. x^4 / ( (x-1)^2*(x^3+x^2+x-1)^2 ). %F A118885 a(n) -2*a(n-1) + a(n-2) = A073778(n). - _R. J. Mathar_, Jul 26 2022 %e A118885 a(5)=4 because we have 00110,00111,00011 and 10011. %p A118885 g:=z^4/(1-2*z+z^4)^2: gser:=series(g,z=0,40): seq(coeff(gser,z,n),n=0..36); %Y A118885 Cf. A118884. %K A118885 nonn %O A118885 0,6 %A A118885 _Emeric Deutsch_, May 03 2006