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 A070430 #32 Dec 07 2019 12:18:23
%S A070430 0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,
%T A070430 1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,
%U A070430 4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0,1,4,4,1,0
%N A070430 a(n) = n^2 mod 5.
%C A070430 Equivalently n^6 mod 5. - _Zerinvary Lajos_, Nov 06 2009
%H A070430 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,1).
%F A070430 From _R. J. Mathar_, Apr 20 2010: (Start)
%F A070430 a(n) = a(n-5).
%F A070430 G.f.: -x*(1+x)*(x^2+3*x+1) / ( (x-1)*(1+x+x^2+x^3+x^4) ). (End)
%t A070430 Table[Mod[n^2,5],{n,0,200}] (* _Vladimir Joseph Stephan Orlovsky_, Apr 21 2011 *)
%t A070430 PowerMod[Range[0, 200], 2, 5] (* _G. C. Greubel_, Mar 22 2016 *)
%o A070430 (Sage) [power_mod(n,2,5)for n in range(0, 101)] # _Zerinvary Lajos_, Nov 06 2009
%o A070430 (Sage) [power_mod(n,6,5)for n in range(0, 101)] # _Zerinvary Lajos_, Nov 06 2009
%o A070430 (PARI) a(n)=n^2%5 \\ _Charles R Greathouse IV_, Sep 28 2015
%Y A070430 Cf. A053879, A070431, A070432.
%K A070430 nonn,easy
%O A070430 0,3
%A A070430 _N. J. A. Sloane_, May 12 2002