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 A070464 #19 Dec 18 2023 13:08:48
%S A070464 0,1,4,9,16,25,36,7,22,39,16,37,18,1,28,15,4,37,30,25,22,21,22,25,30,
%T A070464 37,4,15,28,1,18,37,16,39,22,7,36,25,16,9,4,1,0,1,4,9,16,25,36,7,22,
%U A070464 39,16,37,18,1,28,15,4,37,30,25,22,21,22,25,30,37,4,15,28,1,18,37,16,39
%N A070464 a(n) = n^2 mod 42.
%H A070464 Vincenzo Librandi, <a href="/A070464/b070464.txt">Table of n, a(n) for n = 0..1400</a>
%H A070464 <a href="/index/Rec#order_42">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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
%F A070464 a(n) = a(n-42). - _G. C. Greubel_, Mar 25 2016
%t A070464 Table[Mod[n^2,42],{n,0,200}] (* _Vladimir Joseph Stephan Orlovsky_, Apr 27 2011 *)
%t A070464 PowerMod[Range[0,80],2,42] (* _Harvey P. Dale_, Mar 13 2019 *)
%o A070464 (Magma) [n^2 mod 42: n in [0..80]]; // _Vincenzo Librandi_, Apr 27 2011
%o A070464 (PARI) a(n)=n^2%42 \\ _Charles R Greathouse IV_, Apr 06 2016
%Y A070464 Cf. A070461, A070462, A070463.
%K A070464 nonn,easy
%O A070464 0,3
%A A070464 _N. J. A. Sloane_, May 12 2002