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 A011658 #54 Jun 24 2023 16:03:11
%S A011658 0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,
%T A011658 1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,1,1,0,0,0,
%U A011658 1,1,0,0,0,1,1,0,0,0,1,1,0
%N A011658 Period 5: repeat [0, 0, 0, 1, 1]; also expansion of 1/(x^4 + x^3 + x^2 + x + 1) (mod 2).
%C A011658 Sequences of period k composed of (k-p) zeros followed by p ones have a closed formula of floor((n mod k)/(k-p)) for p >= floor(k/2). - _Gary Detlefs_, May 18 2011
%C A011658 a(n+3) is the determinant of an n X n pentadiagonal symmetric Toeplitz matrix with a=b=c=1. - _R. J. Mathar_, Jan 31 2023
%H A011658 J. Borowska and L. Lacinska, <a href="https://doi.org/10.17512/jamcm.2014.4.03">Recurrence form of determinant of a heptadiagonal symmetric Toeplitz matrix</a>, J. Appl. Math. Comp. Mech. 13 (2014) 19-16, remark 1 for determinant of Toeplitz matrices a=b=c=1.
%H A011658 R. Gold, <a href="http://dx.doi.org/10.1137/0114079">Characteristic linear sequences and their coset functions</a>, J. SIAM Applied. Math., 14 (1966), 980-985.
%H A011658 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%H A011658 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,1).
%F A011658 a(n) = floor((n mod 5)/3). - _Gary Detlefs_, May 18 2011
%F A011658 a(n+2) = A198517(n+4) - A198517(n+2) + A198517(n). - _Bruno Berselli_, Nov 02 2011
%F A011658 a(n+4) = abs(a(n) - a(n+1) + a(n+2) - a(n+3)). - _Benjamin Knight_, May 06 2018
%F A011658 a(n) = (2/5) * (1 + cos(4*(n-4)*Pi/5) + cos(2*(n-3)*Pi/5) + cos(4*(n-3)*Pi/5) + cos(2*(n+1)*Pi/5)). - _Wesley Ivan Hurt_, Sep 26 2018
%F A011658 G.f.: -x^3*(1+x) / ( (x-1)*(1+x+x^2+x^3+x^4) ). - _R. J. Mathar_, Aug 11 2021
%F A011658 a(n) = floor(2*n/5) - 2*floor(n/5). - _Ridouane Oudra_, Apr 01 2023
%p A011658 seq(floor(2*n/5) - 2*floor(n/5), n=0..100); # _Ridouane Oudra_, Apr 01 2023
%t A011658 PadRight[{},120,{0,0,0,1,1}] (* _Harvey P. Dale_, Dec 16 2015 *)
%o A011658 (PARI) a(n)=(n%5)\3 \\ _Charles R Greathouse IV_, Jan 16 2017
%Y A011658 Cf. A198517. Parity of A010891(n+2).
%K A011658 nonn,easy
%O A011658 0,1
%A A011658 _N. J. A. Sloane_