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 A070440 #24 Apr 06 2016 18:04:22
%S A070440 0,1,4,9,16,7,0,13,10,9,10,13,0,7,16,9,4,1,0,1,4,9,16,7,0,13,10,9,10,
%T A070440 13,0,7,16,9,4,1,0,1,4,9,16,7,0,13,10,9,10,13,0,7,16,9,4,1,0,1,4,9,16,
%U A070440 7,0,13,10,9,10,13,0,7,16,9,4,1,0,1,4,9,16,7,0,13,10,9,10,13,0,7,16,9
%N A070440 a(n) = n^2 mod 18.
%H A070440 G. C. Greubel, <a href="/A070440/b070440.txt">Table of n, a(n) for n = 0..1000</a>
%H A070440 <a href="/index/Rec#order_18">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
%F A070440 a(n) = a(n-18). - _R. J. Mathar_, Jul 27 2015
%F A070440 G.f.: -x*(1 +4*x +9*x^2 +16*x^3 +7*x^4 +13*x^6 +10*x^7 +9*x^8 +10*x^9 +13*x^10 +7*x^12 +16*x^13 +9*x^14 +4*x^15 +x^16) / ( (x-1)*(1+x+x^2)*(1+x^3+x^6)*(1+x)*(1-x+x^2)*(1-x^3+x^6) ). - _R. J. Mathar_, Jul 27 2015
%t A070440 Table[Mod[n^2,18],{n,0,200}] (* _Vladimir Joseph Stephan Orlovsky_, Apr 23 2011 *)
%o A070440 (PARI) a(n)=n^2%18 \\ _Charles R Greathouse IV_, Apr 06 2016
%Y A070440 Cf. A070441, A070442.
%K A070440 nonn,easy
%O A070440 0,3
%A A070440 _N. J. A. Sloane_, May 12 2002