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 A021420 #20 Sep 05 2025 01:03:03
%S A021420 0,0,2,4,0,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,
%T A021420 5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,
%U A021420 6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6,1,5,3,8,4,6
%N A021420 Decimal expansion of 1/416.
%C A021420 Period 6: after 0.00240, 384615 repeats endlessly. - _Alonso del Arte_, Apr 26 2018
%H A021420 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,-1,1).
%F A021420 From _Chai Wah Wu_, Sep 04 2025: (Start)
%F A021420 a(n) = a(n-1) - a(n-3) + a(n-4) for n > 8.
%F A021420 G.f.: x^2*(-5*x^6 + 8*x^5 - 7*x^4 - 5*x^3 + 4*x^2 - 2*x - 2)/(x^4 - x^3 + x - 1). (End)
%e A021420 0.002403846153846153846153846...
%t A021420 Join[{0, 0}, RealDigits[1/416,10, 104][[1]]] (* _Alonso del Arte_, Apr 26 2018 *)
%t A021420 PadRight[{0,0,2,4,0},120,{8,4,6,1,5,3}] (* _Harvey P. Dale_, May 25 2018 *)
%Y A021420 Cf. A021212 (1/208).
%K A021420 nonn,cons,easy,changed
%O A021420 0,3
%A A021420 _N. J. A. Sloane_