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 A011734 #12 Jun 01 2020 17:40:22
%S A011734 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,
%T A011734 1,0,1,0,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,0,0,0,1,1,0,
%U A011734 1,1,0,0,0,1,1,0,1,1,0,0,0
%N A011734 A binary m-sequence: expansion of reciprocal of x^21 + x^2 + 1 (mod 2, shifted by 20 initial 0's).
%C A011734 Sequence is 2^21-1 = 2097151-periodic. - _M. F. Hasler_, Feb 17 2018
%D A011734 S. W. Golomb, Shift-Register Sequences, Holden-Day, San Francisco, 1967.
%D A011734 H. D. Lueke, Korrelationssignale, Springer 1992, pp. 43-48.
%D A011734 F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier/North Holland, 1978, p. 408.
%F A011734 G.f. = x^20/(x^21 + x^2 + 1), over GF(2). - _M. F. Hasler_, Feb 17 2018
%t A011734 Join[PadRight[{},20,0],(Mod[#,2]&/@CoefficientList[Series[1/(x^21+x^2+1),{x,0,60}],x])] (* _Harvey P. Dale_, Jun 01 2020 *)
%o A011734 (PARI) A=matrix(N=21,N,i,j, if(i>1, i==j+1, setsearch([2,N], j)>0))*Mod(1,2); a(n)=lift((A^(n-#A+1))[1,1]) \\ _M. F. Hasler_, Feb 17 2018
%Y A011734 Cf. A011655..A011745 for other binary m-sequences, and A011746..A011751 for similar expansions over GF(2).
%K A011734 nonn
%O A011734 0,1
%A A011734 _N. J. A. Sloane_
%E A011734 Edited by _M. F. Hasler_, Feb 17 2018