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 A212016 #18 Jan 05 2016 16:58:12
%S A212016 1,2,5,6,10,13,14,15,19,25,28,29,30,31,35,41,44,50,54,55,56,60,61,69,
%T A212016 77,85,86,90,91,92,96,105,110,113,121,126,135,139,140,141,145,146,149,
%U A212016 154,170,174,181,182,190,194,195,199,203,204,205,209,218
%N A212016 Sums of the squares of two or more consecutive integers.
%C A212016 Subsequence of A062861.
%C A212016 Contains A212015 as a subsequence.
%C A212016 A174069 is a subsequence. - _Altug Alkan_, Dec 24 2015
%H A212016 Robert Israel, <a href="/A212016/b212016.txt">Table of n, a(n) for n = 1..10000</a>
%p A212016 N:= 1000: # to get all terms <=N
%p A212016 g:= x -> x*(x+1)*(2*x+1)/6:
%p A212016 S:= select(`<=`,{seq(seq(g(b)-g(a), a= -b-1 .. b-2), b = 1..floor((sqrt(2*N-1)+1)/2))},N):
%p A212016 sort(convert(S,list)); # _Robert Israel_, Jan 05 2016
%o A212016 (PARI) { isA212016(t) = fordiv(6*t,k, if(k==1,next); z=(k^2-1)/3; if(issquare(4*t/k-z), return(k)); if(z>4*t/k,break); ); 0 }
%Y A212016 Cf. A062861, A174069, A212015.
%K A212016 nonn,easy
%O A212016 1,2
%A A212016 _Max Alekseyev_, Apr 26 2012