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 A159852 #10 Jun 19 2018 11:28:44
%S A159852 0,1,4,9,16,25,36,49,4,21,40,1,24,49,16,45,16,49,24,1,40,21,4,49,36,
%T A159852 25,16,9,4,1,0,1,4,9,16,25,36,49,4,21,40,1,24,49,16,45,16,49,24,1,40,
%U A159852 21,4,49,36,25,16,9,4,1,0,1,4,9,16,25,36,49,4,21,40,1,24,49,16,45,16,49,24,1
%N A159852 n^2 mod 60.
%C A159852 Periodic with period 30: a(n+30) = a(n);
%C A159852 a(15*n+k) = a(15*n-k) for k<=15*n;
%C A159852 a(m*n) = a(m)*a(n) mod 60;
%C A159852 A010421 gives the range of this sequence.
%H A159852 <a href="/index/Rec#order_30">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, 1).
%t A159852 LinearRecurrence[{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},{0, 1, 4, 9, 16, 25, 36, 49, 4, 21, 40, 1, 24, 49, 16, 45, 16, 49, 24, 1, 40, 21, 4, 49, 36, 25, 16, 9, 4, 1},80] (* _Ray Chandler_, Aug 26 2015 *)
%t A159852 PowerMod[Range[0,80],2,60] (* or *) PadRight[{},80,{0,1,4,9,16,25,36,49,4,21,40,1,24,49,16,45,16,49,24,1,40,21,4,49,36,25,16,9,4,1}] (* _Harvey P. Dale_, Jun 19 2018 *)
%o A159852 (PARI) a(n)=n^2%60 \\ _Charles R Greathouse IV_, May 09 2013
%Y A159852 Cf. A070431, A008959, A070435, A070438, A070442, A070452, A000290.
%K A159852 nonn,easy
%O A159852 0,3
%A A159852 _Reinhard Zumkeller_, Apr 24 2009